 |
Secondly, Whereas the French Author is of opinion, that 'tis unknown, how much time a Heavy Body requires to sink in water, according to a certain depth; he may please to take notice, that that hath been made out in England by frequent Experiments; by which, several Depths, found by this Method of sounding without a Line, were examin'd by trying them over again in the same place with a Line, after the common way. And as to that Quaere of his, Whether a heavy Body descends in the same Proportion of swiftness in Water, that it would do in Air? The Answer is, that it does not; but that, after it is sunk one or two fathoms into the Water, it has there arrived to its greatest swiftness, and keeps, after that, an equal degree of velocity; the Resistance of the water being then found equal to the Endeavour of the heavy Body downwards.
Thirdly, When the same Author alledges that it must be known, when a Light Body reascends from the bottom of the water to {230} the top, in what proportion of time and swiftness it rises. He seems not to have considered, that in this Experiment, the times of the descent and assent are both taken and computed together; so that for this purpose, there needs not that nicety, he discourses of.
Fourthly, Whereas it is further excepted, That this way of Sounding Depths is no new Invention; The answer is ready, that neither is it pretended to be so, in the often quoted Tract; it being only intimated there, that the manner of performing it, as it is in that place represented and described, is new.
Lastly, To rectifie the said Author's mistake, as if the instrument of fetching up Water from the bottom of the Sea, were chiefly contriv'd, to find out, Whether in some places of the Sea any Sweet Water is to be met with at the bottom: There will need no more, than to direct him to the Book it self Num. 9. where p. 149. towards the end, the First use of this Bucket is express'd to be, to know the degrees of Saltness of the Water according to its nearness to the top or bottom; or rather to know the constitution of the Sea-water in several depths of several Climates, which is a matter, much better to be found out by Trial, than Discourse. Neither is it any where argued in that Book (as the French Journal insinuates) that, because sweet water is found at the Bottom of the Sea of Baharem, therefore it must, but only that it may, be found so elsewhere. And since the same Journal admits, that those Sweet water-springs, which yield the sweet water, that is found at the said place, have been formerly on the Continent, far enough from the Sea, which hath afterwards covered them. It will be, it is presumed, lawful to ask, Why in many other places there may not be found the like? And besides, how we do know, but that there may be in other parts, Eruptious of large Springs at the bottom of the Sea, as well as there?
* * * * *
Printed with Licence for John Martyn, and James Allestry, Printers to the Royal-Society. 1666.
{231}
* * * * *
Num. 14.
PHILOSOPHICAL TRANSACTIONS.
* * * * *
Munday, July 2. 1666.
* * * * *
The Contents.
An Account of a New kind of Baroscope, which may be call'd Statical; and of some Advantages and Conveniencies it hath above the Mercurial; communicated by Mr. Boyle. The Particular Observations of the Planet Mars, formerly intimated to have been made by Mr. Hook in February and March last. Some Observations, made in Italy, confirming the former; and withall fixing the Period of the said Planet's Revolution. Observations, lately made at London, of the Planet Jupiter: as also of Saturn. A Relation of a sad Effect of Thunder and Lightning. An Account of some Books, lately publish'd; videl. The Relations of divers Curious Voyages, by Mons. Thevenot: A Discourse about the Cause of the Inundation of the Nile, by Mons. de la Chambre, both French: De Principiis & Ratiocinatione Geometrarum, Contra Fastum Professerum Geometriae, by Mr. Hobbes: King Salomons Pourtraiture of Old Age, by J. Smith, M. D.
* * * * *
An Account of a New kind of Baroscope, which may be called Statical; and of some Advantages and Conveniencies it hath above the Mercurial: Communicated, some while since, by the Honourable Robert Boyle.
[Sidenote: * See Num. 11. p. 185. Phil. Transactions.]
As for the New kind of Baroscopes, which, not long agoe, * I intimated to you, that my haste would not permit me to give you an account off; since your Letters acquaint me, that you still design a Communicating to the {232} Curious as much Information, as may be, in reference to Baroscopes; I shall venture to send you some Account of what I did but name (in my former Letter) to you.
[Sidenote: * The Scales here meant were before competent Eyewitnesses made to turn manifestly with the thousandth part of a grain.]
Though by a Passage, you may meet with in the 19th and 20th Pages of my Thermometrical Experiments and Thoughts, you may find, that I did some years agoe think upon this New kind of Baroscope; yet the Changes of the Atmosphere's Weight not happening to be then such, as I wish'd, and being unwilling to deprive my self of all other use of the exactest Ballance *, that I (or perhaps any man) ever had, I confess to you, that successive avocations put this attempt for two or three years out of my thoughts; till afterwards returning to a place, where I chanc'd to find two or three pairs of Scales, I had left there, the sight of them brought it into my mind; and though I were then unable to procure exacter, yet my desire to make the Experiment some amends for so long a neglect, put me upon considering, that if I provided a Glass-buble, more than ordinary large and light, even such Ballances, as those, might in some measure perform, what I had tried with the strangely nice ones above-mention'd.
I caused then to be blown at the Flame of a Lamp some Glass-bubles as large, thin and light, as I could then procure, and choosing among them, one, that seem'd the least unfit for my turn, I counterpoised it in a pair of Scales, that would loose their AEquilibrium with about the 30th part of a Grain, and were suspended at a Frame. I placed both the Ballance and the Frame by a good Baroscope, from whence I might learn the present weight of the Atmosphere. Then leaving these Instruments together; though the Scales, being no nicer than I have express'd, were not able to shew me all the Variations of the Air's weight that appear'd in the Mercurial Baroscope, yet they did what I expected, by shewing me variations no greater, than alter'd the height of Quicksilver half a quarter of an Inch, and perhaps much smaller than those: Nor did I doubt, that, if I had had either tender Scales, or the means of supplying the experiment with convenient accommodations, I should have {233} discerned far smaller Alterations of the Weight of the Air, since I had the pleasure to see the Buble sometimes in an aequilibrium with the counterpoise; sometimes, when the Atmosphere was high, preponderate so manifestly, that the Scales being gently stirr'd, the Cock would play altogether on that side, at which the Buble was hung; and at other times (when the Air was heavier) that, which was at the first but the Counterpoise, would preponderate, and, upon the motion or the Ballance, make the Cock vibrate altogether on its side. And this would continue sometimes many daies together, if the Air so long retain'd the same measure of gravity; and then (upon other changes) the Buble would regain an aequilibrium, or a preponderance; so that I had oftentimes the satisfaction, by looking first upon the Statical Baroscope (as for distinctions sake it may be call'd) to foretell, whether in the Mercurial Baroscope the Liquor were high or low. Which Observations though they hold as well in Winter, and several times in Summer (for I was often absent during that season) as the Spring, yet the frequency of their Vicissitudes (which perhaps was but accidental) made them more pleasant in the latter of these seasons.
So that, the matter of Fact having been made out by variety of repeated Observations, and by sometimes comparing severall of those new Baroscopes together, I shall add some of those Notes about this Instrument, which readily occur to my memory, reserving the rest till another opportunity.
And First, if the ground, on which I went in framing this Baroscope, be demanded, the answer in short may be; 1. That, though the Glass-buble, and the Glass-counterpoise, at the time of their first being weigh'd, be in the Air, wherein they both are weigh'd, exactly of the same weight; yet they are nothing near of the same bulk; the Buble, by reason of its capacious cavity (which contains nothing but Air, or something that weighs less than Air) being perhaps a hundred or two hundred times (for I have not conveniency to measure them) bigger than the Metalline counterpoise. 2. That according to a Hydrostatical Law (which you know I have lately had occasion to make out) If two Bodies of equal gravity, but unequal bulk come to be weigh'd in another Medium, they will be no longer {234} equiponderant; but if the new Medium be heavier, the greater Body, as being lighter in Specie, will loose more of its weight, than the lesser and more compact; but if the new Medium be lighter than the first, then the bigger Body will outweigh the lesser; And this disparity, arising from the change of Medium's, will be so much the greater, by how much the greater inequality of bulk there is between the Bodies formerly equiponderant. 3. That, laying these two together, I consider'd, that 'twould be all one, as to the effect to be produced, whether the Bodies were weighed in Mediums of differing gravity, or in the same Medium, in case its (specifick) gravity were considerably alter'd: And consequently, that since it appear'd by the Baroscope, that the weight of the Air was sometimes heavier, and sometimes lighter, the alterations of it, in point of gravity, from the weight, it was off at first counterpoising of the Buble of it, would unequally affect so large and hollow a Body, as the Buble, and so small and dense a one, as a Metallin weight: And when the Air by an increase of gravity should become a heavier Medium, than before, it would buoy up the Glass more than the Counterpoise; and if it grew lighter, than it was at first, would suffer the former to preponderate: (The Illustrations and Proof can scarce be added in few words; but, if it be desired, I may, God permitting, send you them at my next leasure:) And though our English Air be about a thousand times lighter, than water, the difference in weight of so little Air, as is but equal in bulk to a Buble, seem'd to give small hopes, that it would be sensible upon a Ballance; yet, by making the Buble very large and light, I supposed and found the Event, I have already related.
Secondly, The hermetically seal'd Glass-buble, I employed, was of the bigness of a somewhat large Orange, and weigh'd about 1. drachme and 10. grains. But I thought it very possible, if I had been better furnish'd with conveniencies (wherein I afterwards found, I was not mistaken) to make (among many, that might be expected to miscarry) some, that might be preferable to this, either for capacity or lightness, or both; especially if care be taken, that they be not seal'd up, whilst they are too hot. For, though one would think, that it were {235} advantagious to rarify and drive out the Air as much as is possible, because in such seal'd Bubles the Air it self (as I have elsewhere shewn) has a weight; yet this advantage countervails not the inconvenience of being obliged to increase the weight of the Glass, which when it includes highly rarified Air, if it be not somewhat strong, will be broken by the pressure of the External Air, as I have sufficiently tryed.
Thirdly, I would have tryed, whether the Dryness and Moisture of the Air would in any measure have alter'd the weight of the Buble, as well as the Variation of Gravity produced in the Atmosphere by other causes; but the extraordinarily constant absence of Fogs, kept me from making Observations of this kind; save that one morning early, being told of a mist, I sent to see (being my self in bed) whether it made the Air so heavy as to buoy up the Buble; but did not learn, that that mist had any sensible operation on it.
Fourthly, By reason of the difficulties and casualties, that may happen about the procuring and preserving such large and light Bubles, as I have been lately mentioning; it may in some cases prove a convenience to be inform'd, That I have sometimes, instead of one sufficiently large Buble, made use of two, that were smaller. And, though a single Buble of competent bignes be much preferable, by reason that a far less quantity and weight of Glass is requisite to comprise an equal capacity, when the Glass is blown into a single Buble, than when it is divided into two; yet I found, that the employing of two instead of one, did not so ill answer my exspectations, but that they may for a need serve the turn instead of the other; than which they are more easier to be procured; And if the Ballance be strong enough to bear so much Glass, without being injur'd: by employing two or a greater number of large Bubles, the effect may be more conspicuous, than if only a single Buble (though a very good one) were employed.
This instrument may be much improved by divers Accommodations, As
First, There may be fitted to the Ansa (or Checks of the Ballance) an Arch (of a Circle) divided into 15. or 20. deg. (more or less, according to the goodness of the Ballance) that the Cock resting over against these Divisions, may readily {236} and without Calculation shew the quantity of the Angle, by which, when the scales propend either way, the Cock declines from the Perpendicular, and the beam from its Horizontall parallelism.
Secondly, Those, that will be so curious, may, instead of the Ordinary Counterpoise (of Brass) employ one of Gold, or at least of Lead, whereof the latter being of equal weight with Brass, is much less in Bulk, and the former amounts not to half its bigness.
Thirdly, These parts of the Ballance, that may be made of Copper or Brass, without any prejudice to the exactness, will, by being made of one of those Mettals, be less subject, than Steel, (which yet, if well hardned and polish'd, may last good a great while) to rust with long standing.
Fourthly, Instead of the scales, the Buble may be hung at one end of the Beam, and only a Counterpoise to it at the other, that the Beam may not be burthen'd with unnecessary weight.
Fifthly, The whole instrument, if placed in a small Frame, like a square Lanthorn with Glass-windows, and a hole at the top for the Commerce of the internal and external Air, will be more free from dust, and irregular agitations; to the latter of which, it will otherwise be sometimes incident.
Sixthly, This instrument being accommodated with a light Wheele and an Index (such as have been applyed by the excellent Dr. Chr. Wren to open Weather glasses, and by the ingenious Mr. Hook to Baroscopes) may be made to shew much more minute variations, than otherwise.
Seventhly, And the length of the Beam, and exquisitness of the Ballance, may easily, without any of the foregoing helps (and much more with them) make the instrument far exacter, than any of those, I was reduced to employ. And to these Accommodations divers others may be suggested by a farther consideration of the nature of the thing, and a longer practice.
Though in some respects this Statical Baroscope be inferior to the Mercurial; yet in others it has its own advantages and conveniencies above it.
And 1: It confirms ad oculum our former Doctrine, that the falling and rising of the Mercury depends upon the varying weight of the Atmosphere; since in this Baroscope it cannot {237} be pretended, that a Fuga vacui, or a Funiculus, is the cause of the changes, we observe. 2. It shews, that not only the Air has weight, but a more considerable one, than some Learned men, who will allow me to have prov'd, it has some weight, will admit; since even the variation of weight in so small a quantity of Air, as is but equal in bulk to an Orange, is manifestly discoverable upon such Balances, as are none of the nicest. 3. This Statical Baroscope will oftentimes be more parable, than the other: For many will finde it more easie, to procure a good pair of Gold-scales, and a Buble or two, than a long Cane seal'd, a quantity of Quick-silver, and all the other requisits of the Mercurial Baroscope; especially if we comprise the trouble and skill, that is requisite to free the deserted part of the Tube from Air. 4. And whereas the difficulty of removing the Mercurial Instrument has kept men from so much as attempting to do it, even to neighbouring places; the Essential parts of the Scale-Baroscope (for the Frame is none of them) may very easily in a little room be carried, whither one will, without the hazard of being spoil'd or injur'd. 5. There is not in Statical Baroscopes, as in the other, a danger of uncertainty, as to the goodness of the Instruments, by reason, that in these the Air is, in some more, and in some less perfectly excluded; whereas in those, that consideration has no place. (And by the way, I have sometimes, upon this account, been able to discover by our new Baroscope, that an esteem'd Mercurial one, to which I compared it, was not well freed from Air.) 6. It being, as I formerly intimated, very possible to discover Hydrostatically, both the bigness of the Buble, and the Contents of the cavity, and the weight and dimensions of the Glassie substance (which together with the included Air make up the Buble,) much may be discover'd by this Instrument, as to the Weight of the Air, absolute or respective. For, when the Quick-silver in the Mercurial Baroscope is either very high, or very low, or at a middle station between its greatest and least height, bringing the Scale-Barometer to an exact AEquilibrium (1 with very minute divisions of a Graine,) you may, by watchfully observing, when the Mercury is risen or faln just an inch, or a fourth, of half an inch &c. and putting in the like minute divisions of a Grain to the lighter Scale, till you have again brought the Ballance to an {238} exquisit AEquilibrium; you may, I say, determine, What known weight in the Statical Baroscope answers such determinate Altitudes of the ascending and descending Quick-silver in the Mercurial. And if the Ballance be accommodated with a divided Arch, or a Wheel and Index, these Observations will assist you for the future to determine readily, by seeing the inclination of the Cock or the degree mark'd by the Index, what pollency the Buble hath, by the change of the Atmospheres weight, acquired or lost. Some Observations of this nature I watchfully made, sometimes putting in a 64^{th.} sometimes a 32^{th.} sometimes a 16^{th.} and sometimes heavier parts of a Grain, to the lighter Scale. But one, that knew not, for what uses those little papers were, coming to a window, where my Baroscopes stood, so unluckily shook them out of the Scales, and confounded them, that he robb'd me of the opportunity of making the nice Observations I intended, though I had the satisfaction of seeing, that they were to be made. 7. By this Statical Instrument we may be assisted to compare the Mercurial Baroscopes of several places (though never so distant) and to make some Estimates of the Gravities of the Air therein. As if, for instance, I have found by Observation, that the Buble, I employ, (and one may have divers Bubles of several sizes, that the one may repaire any mischance, that may happen to another) weigh'd just a Drachme, when the Mercurial Cylinder was at the height of 291/2 inches (which in some places I have found a moderate altitude;) and that the Addition of the 16th part of a gr. is requisite to keep the Buble in an AEquilibrium, when the Mercury is risen an 8th, or any determinate part of an inch above the former station: When I come to another place, where there is a Mercurial Barometer, as well freed from Air as mine (for that must be supposed) if taking out my Scale instrument, it appeare to weigh precisely a Drachme, and the Mercury in the Baroscope there stand at just 291/2 inches, we may conclude the Gravity of the Atmosphere not to be sensibly unequal in both those two places, though very distant. And though there be no Baroscope there, yet if there be an additional weight, as for instance, the 16th part of a Grain requisite to be added to the Buble, to bring the scales to an AEquilibrium, it will appear that the Air at this second place is, at that time {239} so much heavier, than the Air of the former place was, when the Mercury stood at 291/2 inches.
But in making such comparisons, we must not forget to consider the Situation of the several places, if we mean to make Estimates not only of the weight of the Atmosphere, but of the weight and density of the Air. For, though the Scales wil shew (as has been said) whether there be a difference of weight in the Atmosphere at the two places; yet, if one of them be in a Vale or bottom, and the other on the top or some elevated part of a Hill, it is not to be exspected, that the Atmosphere, in this latter place, should gravitate as much, as the Atmosphere in the former, on which a longer Pillar of Air does lean or weigh.
And the mention, I have made of the differing Situation of Places, puts me in mind of something, that may prove another use of our Statical Baroscope, and which I had thoughts of making tryal off, but was Accidentally hindred from the opportunity of doing it. Namely, that by exactly poysing the Buble at the foot of a high Steeple or Hill, and carrying it in its close Frame to the top, one may, by the weight requisite to be added to Counterpoise there to bring the Beam to its Horizontal position, observe the difference of the weight of the Air at the bottom, and at the top; and, in case the Hill be high enough, at some intermediate Stations. But how far this may assist men, to estimate the Absolute or Comparative height of Mountains, and other elevated Places; and what other Uses the Instrument may be put to, when it is duly improved; and the Cautions, that may be requisite in the several cases, that shall be proposed, I must leave to more leasure, and farther Consideration.
* * * * *
The Particulars of those Observations of the Planet Mars, formerly intimated to have been made at London in the Months of February and March A. 1665/6.
To perform, what was promised Num. 11. of these Papers, pag. 198; 'tis thought fit now to publish the Particular Observations, concerning the spots in Mars, and their motion, as they were made with a 36 foot Telescope, and produced in {240} writing before the Royal Society, the 28 March 1666. by Mr. Hook, as follows;
Having a great desire (saith he) to observe the Body of Mars, whilst Acronycal and Retrograde (having formerly with a Glass of about 12. foot long, observ'd some kind of Spots in the Face of it,) though it be not at present in the Perihelium of its Orbe, but nearer its Aphelium, yet I found, that the Face of it, when neer its Opposition to the Sun (with a Charge, the 36. foot-glass, I made use off, would well bear) appear'd very near as big, as that of the Moon to the naked eye; which I found, by comparing it with the Full Moon, near adjoyning to it, March 10.
But such had been the ill disposition of the Air for several nights, that from more than 20. Observations of it, which I had made since its being Retrograde, I could find nothing of satisfaction, though I often imagin'd, I saw Spots, yet the Inflective veins of the Air (if I may so call those parts, which, being interspers'd up and down in it, have a greater or less Refractive power, than the Air next adjoyning, with which they are mixt) did make it so confus'd and glaring, that I could not conclude upon any thing.
On the third of March, though the Air were still bad enough yet I could see now and then the Body of Mars appearing of the form A: which I presently described by a Scheme; and about 10. minutes after, as exactly representing what I saw through the Glass, as I could, I drew the Scheme B. This I was sufficiently satisfied (by very often observing it through the Tube, and changing my Eye into various positions, that so there might be no kind of Fallacy in it) could be nothing else, but some more Dusky and Spotted parts of the Face of this Planet.
March 10. finding the Air very bad, I made use of a very shallow Eye-glass, as finding nothing Distinct with the greater Charge; and saw the appearance of it as in C, which I imagin'd, might be the Representation of the former Spots by a lesser charge. About 3 of the Clock the same morning, the Air being very bad (though to appearance exceeding clear, and causing all the Stars to twinckle, and the minute Stars to appear very thick) the body seem'd like D; which I still suppos'd to be {241} the Representation of the same Spots through a more confused and glaring Air.
But observing March 21. I was surprised to find the Air (though not so clear, as to the appearance of small Stars) so exceeding transparent, and the Face of Mars so very well defined, and round, and distinct, that I could manifestly see it of the shape in E. about half an hour after Nine at night. The Triangular spot on the right side (as it was inverted by the Telescope, according to the appearances, through with all the preceeding Figures are drawn) appear'd very black and distinct, the other towards the left more dim; but both of them sufficiently plain and defin'd. About a quarter before 12. of the Clock the same night, I observ'd it again with the same Glass, and found the appearance exactly, as in F; which I imagin'd to shew me a Motion of the former triangular spot: But designing to observe it again about 3. of the Clock the same Morning, I was hindred by cloudy weather.
But March 22. about half an hour after 8. at night, finding the same Spots in the same posture, I concluded, that the preceeding Observation was only the appearance of the same Spots at another height and thickness of the Air: And thought my self confirm'd in this Opinion, by finding them in much the same posture, March 23. about half an hour after 9. though the Air was nothing so good as before.
And though I desired to make Observations, about 3. of the Clock those mornings; yet something or other interven'd, that hindred me, till March 28. about 3 of the Clock, the Air being light (in weight) though moist and a little hazy; when I plainly saw it, to have the form, represented in I; which is not reconcileable with the other Appearances, unless we allow a Turbinated motion of Mars upon its Center: Which, if such there be, from the Observations made March 21. 22. and 23. we may guess it to be once or twice in about 24. hours unless it may have some kind of Librating motion; which seems not so likely. Now, whether certainly so or not, I shall endeavour, as oft as I have opportunity, further to observe.
A particular direction to the Figures mentioned in the precedent discourse.
A. March 3^{d.} 00^{h.} 20^{m.} in the morning: the Air having many {242} inflecting parts dispersed up and down in it; by the Wheel Barometer, heavy,
B. Another Scheme, which I drew from my Observation, about 10. minutes after, the same morning. Both these were observed with a very deep Eye-glass.
C. March 10^{d.} 00^{h.} 20^{m.} in the morning: the Air heavy and inflective. Use was made of a shallow or ordinary Charge.
D. March 10^{d.} 3^{h.} 00^m in the Morning; the Air very heavy and Inflective, which made it glare and radiate, and be more confused, than about 3. hours before. A shallow Charge.
E. March 21^{d.} 91/2^{h.} post merid; the Air light (in weight) and clear, without inflecting parts; the Face appear'd most distinctly of this Forme. A shallow Charge.
F. March 21^{d.} 113/4^{h.} post merid; the Air continuing very light and clear, without inflecting vapours. A shallow Charge.
G. March 22^{d.} 81/2^{h.} post mer. the Air clear, with few inflecting veins in it, and indifferent light. A shallow Charge.
H. March 23^{d.} 91/2^{h.} post mer. the Air pretty light, but moist, and somewhat thick and hazy, but seem'd to have but few veins, or inflecting parts.
I. March 28^{d.} 3^{h.} p. m. much the same kind of Air with that of March 23; light, moist, and a little hazy, with some very few veins.
* * * * *
Observations made in Italy, confirming the former, and withall fixing the Period of the Revolution of Mars.
These Observations we shall summarily present the Curious in these parts with, as they were lately presented (by Letter from his Excellency the Ambassadour of Venice, now residing at the Court of France) to the Royal Society, in some printed sheets of Paper, entituled, MARTIS, circa Axem proprium Revolubilis, Observationes, BONONIAE a JO. DOMINICO CASSINO habitae; come to hand June 3. 1666.
In these Papers the Excellent Cassini affirms;
1. That with a Telescope of 24. Palmes, or of about 16 Foot, wrought after S. Campani's way, he began to observe February 6. 1666 (st.n.) in the morning, and saw two dark Spots in the first Face of Mars. {243}
2. That with the same Glass he observ'd Febr. 14/24. in the Evening, in the other Face of this Planet, two other Spots, like those of the first, but bigger.
3. That afterwards continuing the Observations, he found the Spots of these two Faces to turn by little and little from East to West, and to return at last to the same situation, wherein he had seen them first.
4. That S. Campani, having also observ'd at Rome with Glasses of 50. Palmes or about 35 Foot, likewise of his own contrivance, had seen in the same Planet the same Phenomena.
5. That sometimes he hath seen, during the same night, the two Faces of Mars, one, in the Evening, the other in the Morning.
6. That the Motion of these Spots in the inferior part of the apparent Hemisphere of Mars, is made from East to West, as that of all the other Celestial Bodies, and is peform'd by Parallels, that decline much from the Equator, and little from the Ecliptick.
7. That the Spots return the next day to the same situation, 40. minuts later, than the day before; so that in every 36. or 37. daies, about the same hour, they come again to the same place.
8. He promises shortly to give us the particular Tables of this Motion and of its Inequalities, together with the Ephemerides themselves.
9. He represents, that some other Astronomers have also made at Rome several Observations of these Spots of Mars, from March 14/24. to March 20/30. with Glasses, wrought by Eustachio Divini, of 25. and 45. Palmes; Which Spots he makes little differing from his own, of the first Face; as will by and by appear, by the direction to the Schemes.
10. But he adds, that those other Roman Astronomers, that have observ'd with Divini's Glasses, will have the Conversion of Mars to be performed, not in 24 h, 40 m. (as he maintains it is) but in about 13 h.
11. And to evince, that they are mistaken in these Observations of theirs; he alledges, That they assure that the Spots, which they have seen in this Planet, (by an Eustachian Telescope) the 20/30 of March, were small, very distant from one another, remote from the middle of the Disk, and the Oriental Spot was less, than the Occidental (as is represented by the Fig. O; like that of the first Face of Mars.) whereas, on the contrary, {244} He (Cassini) pretends to evidence by his Observations, made at the same time at Bononia, that, the same day and hour, those Spots were very large, neer one another, in the midst of the Disk, the Oriental bigger than the Occidental (as appears by Fig. P, which is that of the second Face of Mars.)
12. Besides, he declares, that those Astronomers were too hasty, in determining, after 5 or 6 Observations only, in how much time Mars finish's his Revolution; and denies it to be perform'd in 13 hours: adding, that, though Himself had observ'd for a much longer time, than they; yet he durst not for a great while define, Whether Mars made but one Turn in 24 hours 40 minuts or two; and that all, that he could, for a long time affirm, was onely this, that after 24 h. 40 m. this Planet appear'd in the same manner he did before.
13. But since those first Observations, He affirms to have found cause to determine, that the Period of this Conversion is made in the said space of 24 h. 40 m; and not oftner than once within that time; Alledging for proof;
1. That, whereas Febr. 6. (st.n.) he saw the Spots of the first Face of Mars, moving from eleven of the Clock in the night, until break of day, they appear'd not afterwards in the Evening after the rising of that Planet (witness several intelligent persons, which he names, that were present at the Observations) Whence he infers, that after 12 hours and 20 minuts, the same Spots did not come about; since that the same, which in the morning were seen in the middle, upon the rising of Mars; after 13 or 14 hours, might have appear'd neer the Occidental Limb. But, because he might be imposed upon by Vapors, whilst Mars was yet so neer the Horizon, he gives this other determination, vid.
2. Whereas he saw the first Face of Mars the 6 of February at 11 of the clock of the night following; he did not see the same after 18 daies at the same hour; as he ought to have done, if the Period were absolved in the space of 12 h. 20 m.
3. Again, whereas he saw Febr. 24. in the Evening, the other Face of Mars, he could not see the same, the 13. and 15. day of March, to wit after 17 and 19 days; as he should have done, if the Revolution were made in the newly mention'd time.
4. Again, whereas the 27. of March in the Evening he saw {245} the second Face of Mars, he could not see it the 14. and 16. of April.
From all which Observations he Judges it to be evident, that the Period of this Planets Revolution is not perform'd in the space of 12. hours 20, minutes, but in about 24 hours 40 minutes; more exactly to be determin'd by comparing distant Observations: And that those who affirm the former, must have been deceived by not well distinguishing the two Faces, but that having seen the second, taken it for the first.
All which he concludes with this Advertisement, that, when he defines the time of the Revolution of Mars, he does not speak of its Mean Revolution, but onely of that, which he observ'd, whilst Mars was opposite to the Sun; which is the shortest of all.
_The Figures of the _Principal_ Observations, represented in the Book here discoursed of, may be seen in the annexed _Scheme_; _videl._
K. One of the Faces of Mars, as S. Cassini observed it March 3. (st.n.) 1666 in the Evening, with a Glass of 24 Palmes.
L. The other Face, as he saw it Febr. 14/24 in the Evening.
M. The first Face, as S. Campani saw at Rome, March 3. 1666. in the Evening, with a Glass of 50 Palmes.
N. The second Face, as the same Campani observed it March 18/28. in the Evening.
O. The figure of Mars as it was seen at Rome by a Telescope of Divini of 45 Palmes, March 20/30.
P. The Figure of the said Planet, as it was seen the same day and hour at Bononia by Cassini; being that of the second Face.
* * * * *
Some Observations lately made at London concerning the Planet Jupiter.
These, as they were made, so they were imparted, by Mr. Hook, as follows:
A. 1666, June 26. between 3. and 4. of the Clock in the morning, I observed the Body of Jupiter through a 60 foot-glass, and found the apparent Diameter of it through the Tube, to be somewhat more than 2. degrees, that is, about four {246} times as big, as the Diameter of the Moon appears to the naked Eye. I saw the Limb pretty round, and very well defin'd without radiation. The parts of the Phasis of it had various degrees of Light. About a and f, the North and South poles of it (in the Fig Q.) 'twas somewhat darker, and by degrees it grew brighter towards b. and e, two Belts or Zones; the one of which (b) was a small dark Belt crossing the Body Southward; Adjoyning to which was a smal Line of a somewhat lighter part; and below that again, Southwards, was the great black Belt c. Between that, and e, the other smaller black Belt, was a pretty large and bright Zone; but the middle d, was somewhat darker than the edges. I perceiv'd about 3^{h.} 15^{m.} near the middle of this, a very dark round Spot, like that represented at g, which was not to be perceiv'd about half an hour before: And I observed it, in about 10. minutes time to be gotten almost to d, keeping equal distance from the Satelles h, which moved also Westwardly, and was joyn'd to the Disk at i, at 3^{h.} 25^{m.} After which, the Air growing very hazy, and (as appeared by the Baroscope) very light also (in weight) I could not observe it: So that it was sufficiently evident, that this black Spot was nothing else, save the shadow of the Satelles h, Eclipsing a part of the Face of Jupiter. About two hours before, I had observed a large darker spot in the bigger Belt about k, which in about an hour or little more (for I did not exactly observe the time, nor draw the Figure of it) moving Westwards, disappear'd. About a week before, I discover'd also, together with a Spot in the Belt c, another Spot in the Belt e, which kept the same way and velocity with that of the Belt c. The other three Satellites in the time of this Eclipse, made by the Satelles, were Westwards of the Body of Jupiter; appearing as bright through the Tube, as the Body of Jupiter did to the naked Eye, and I was able to see them longer through the Tube, after the day-light came on, than I was able to see the Body of Jupiter with my naked eye.
* * * * *
A late Observation about Saturn made by the same.
June 29 1666. between 11. and 12. at night I observed the Body of Saturn through a 60. foot Telescope, and found it {247} exactly of the shape represented in the Figure R. The Ring appear'd of a somewhat brighter Light than the Body; and the black lines a a, crossing the Ring, and b b crossing the Body (whether Shadows or not, I dispute not) were plainly visible: whence I could manifestly see, that the Souther-most part of the Ring was on this side of the Body, and the Northern part, behind, or covered by the Body.
* * * * *
A Relation of a sad effect of Thunder and Lightning:
This Relation was written by that worthy Gentleman, Thomas Neale Esquire, (the then High Sheriff of the County of Hampshire, when this disaster hapned) to a Friend of his in London, as follows;
On the 24 of January 1665/6, one Mr. Brooks of Hampshire, going from Winchester towards his house near Andover in very bad Weather, was himself slain by Lightning, and the Horse, he rode on, under him. For about a mile from Winchester he was found with his Face beaten into the ground, one leg in the stirrup, the other in the Horses mane; his Cloaths all burnt off his back, not a piece as big as a handkerchief left intire, and his hair and all his body singed. With the force, that struck him down, his nose was beaten into his face, and his Chin into his Breast; where was a wound cut almost as low, as to his Navil; and his cloaths being, as aforesaid, torn, the pieces were so scatter'd and consum'd, that not enough to fill the crown of a hat could be found. His gloves were whole, but his hands in them sing'd to the bone. The hip-bone and shoulder of his Horse burn't and bruised; and his saddle torn in little pieces. This was what appear'd to the Coroners inquest, and so is likely to be as near truth, as any is to be had.
So far this Letter: Which, if it had come soon enough to the hands of the Publisher, would have been joyned to a like Relation, inserted in the next foregoing Papers (Num. 13.) of an accident hapn'd at a later time. With both which may be compared the Account, formerly published in Latin by the Learned Dr. Charleton, concerning the Boy, that was {248} Thunder-struck near Nantwich in Cheshire; the Title of the Book being Anatome Pueride Caelo tacti: such Relations, when truly made, well deserving to be carefully recorded for farther consideration.
* * * * *
Of some Books lately publish't.
RELATIONS OF DIVERS CURIOUS VOYAGES, by Mons. Thevenot, the third Tome, in French. This Book contains chiefly, the Ambassie of the Dutch into China, translated out of the Dutch manuscript: A Geographical description of China, translated out of a Chinese Author by Martinius: And the Account, which the Directors of the Dutch East-India Company made to the States General, touching the state of affairs in the East-Indies, when their late Fleet parted from thence. To touch some things of a Geographical and Philosophical nature, contained therein, we shall take notice;
1. How the Kingdom of China is peopled; there being according to the best computation (which is there made with singular care) above 58 millions of Men, not counting Magistrates, Soldiers, Priests, Eunuchs, Women and Children; so that it may not be altogether strange, if one should affirm, there were 200 millions of people, of all sorts, in that Kingdom.
2. That Catay is nothing else, but the Six Northern Provinces of China, separated from the other Nine, by the great River KIANG; and that the City Cambalu is the same with that of Peking; the Tartars, who carry every three years their Tribute to the Emperor of China, constantly calling the said Provinces and City by those names of Catay, and Cambalu.
3. That China is so well furnisht with Rivers, and cut Channels, that men may go from the most Southern to the most Northern part thereof by water, except one daies journey; as the Dutch Ambassadours did, embarking at Canton, which is 23d. 48m. Northern Latitude, and landing at Peking, which is about 40d; having only travell'd one daies journey over some Mountains of the Province Kiamsi.
4. That the people of China are exceeding industrious {249} Husbandmen making, among other waies of improving their soile, great use of Flouding.
5. That the Physicians of China do cure Sicknesses with much ease, and in a short time: That they have very ancient Books of the nature and vertues of Herbs, Trees and Stones: That their Modern Physicians (as well as their Ancient ones did) write of the Prognosticks, Causes, Effects, &c. of Diseases. That their Remedies consist for the most part of Simples and Decoctions, Cauteries, Frictions; without the use of Bloud letting: That they have such an excellent skill and method in feeling the Pulse, that by the means thereof they discover even the most latent causes of Diseases; taking a good half hour, when they visit a Patient, in feeling and examining his Pulse: That they prescribe much the use of The; and the drinking alwayes warme, whatever they drink: To the custome of both which it's imputed, that the inhabitants of China do spit very little, nor are subject to the Stone or Gout: That they prise highly the Root Ginseng, as an extraordinary Restorative and Cordiall, recovering frequently with it agonizing persons; one pound of it being paid with 3 pounds of silver. As for their Chymists, (of which they have also good store) they go beyond ours, promising not only to make Gold, but to give Immortality.
6. That their Nobility is raised from Learning and Knowledge, without regard to Bloud or Parentage, excepting the Royall Family.
7. That in CHEKIAN, a maritime Province, whence is the shortest cut of China to Japan, is the best and plentifullest Silk-trade in the world: And that there every year the Mulberries are cutt, and kept down, that they grow not into Trees for the easier gathering of the Leaves, there being a double Silk-harvest in that Country, as there is in severall other parts of the East-indies; (both which there is hope, will shortly be imitated in Virginia.)
8. That the way of making Porcelane is this: (Which is the rather inserted here, because it agrees so well with an Account, we received a while since from a very Curious and intelligent Person of Amsterdam.) There is in the Province of Nankin a Town, call'd {250} Goesifols whence they draw the Earth for Porcelaine, which is found between the Rocks of Mountains. This Earth they beat very small, and stamp it to a very fine Powder, and then put it into Tubs fill'd with water; where the finest part sinks to the bottom. Afterwards 'tis kneaded in the form of small Cubes, of the weight of about 3. Catti (a Catti being 20 Ounces.) These pieces thus wrought are sold to the people, that commonly in great numbers fetch them, coming from the Town Sintesimo (otherwise Jontiou) in the Province of Kiansy, being about 50 miles distant from Wotsing, neer the City KIANSY; which people transport them to their homes, and there bake them in this manner: They heat their Ovens well, for the space of 15 daies successively, and then keep them so close, that no Air may get in; and after 15 other daies are pass'd, they open the Oven in the presence of an Officer, who takes every fifth vessel of each fashion for the service of the Emperor: Which done, the rest is sold to those of Ucienien, whence it is transported all over the Country. So that the Earth is not prepared, in Nankin, where 'tis found, because the people of that Province have not the skill of working it, as the other above-mention'd; who also alone have the Art of coloring it, which they keep as a great Secret, not teaching it to any, but their Children and next Kindred.
9. That Musk is nothing else, but the Testicles of a Beast like a Dear, found in the Province of Honan; and that, when tis good and unmixt, as it comes from the Animal, they sell it even in Nankin and Pekin, for 30. or 35. Teyls (that is, about so many Crowns) the Catti.
Many other curious informations might be borrow'd from this Author, concerning the Customs, Studies, Exercises of the Chinese; of the number of the people of each Province; of the Natural productions of the Earth and Rivers there; of the Structure and Antiquity of their Wall; of the Magnificence of their Porcelain Tower &c.; but, remitting for these things to the Book it self, we shal only add a piece of Oeconomy, used by the Holland-Merchants in their Commerce with China, which is, that they dry abundance of Sage-leaves, role them up, and {251} prepare them like The, and carrying it to China, as a rare drogue, get for one pound of it, fourtimes as much The.
A DISCOURSE ABOUT THE CAUSES OF THE INUNDATION OF THE NILE, in French. The Author of this Book is Monseiur dela Chambre, who being perswaded from several Circumstances, that accompany the Overflowing of this River, that it cannot proceed from Rain, ventures to assign for a Cause of it, and of all the other effects that happen at the time of its swelling, the Niter, wherewith that water abounds.
The discourse having six parts, the Author endeavours to shew in the
First, that the Waters of the Nile are Nitrous, explicating the Nature of Salt, and Saltpeter, and imputing the fertility of the Earth, as well us the fecundity of Animals, to Salt. Where he shews, that all things, that serve to improve Land, are full of Salt; and that 'tis observ'd, that grain steep'd in Vrine, before sowing, rises sooner, and becomes fuller and stronger, than else. Adding, that that, which renders the Seed of Animals prolifick, is, that one of the Spermatick veins hath its Origine from the Emulgent, through which the Nitrous and Saline Serosities, that discharge themselves into the Kidneys and Bladder, do pass.
In the Second, he examins, what is Fermentation, and how 'tis perform'd; affirming, that, what thrusts forth Plants in the Spring, is, that the Earth being fermented by the Niter, it harbours, the Nitrous spirits insinuate themselves into their Pores.
In the Third he treats of all the Circumstances, observable in the Inundation of the Nile. 'Tis affirm'd, that 3 or 4 days before that River begins to overflow, all its water is troubled: that then there falls a certain Dew, which hath a fermenting vertue, and leavens a Paste exposed to the Air: that the Mud, which has been drawn out of the water, grows heavier, when the overflowing begins, then it was before, and that by the increase of the weight of that Mud, they judge of the greatness of the approaching inundation. The Author pretends, that {252} the Niter, which the Nile is stored with, is the cause of all these strange effects, and of many others, by him alledged. For, saith he, when the Nitre is heated by the heat of the Sun, it ferments, and mingling with the water, troubles it, and swells it, and makes it pass beyond its banks; after the same manner, as the Spirits in new Wine render it troubled, and make it boyle in the vessel. And it seems not likely to him, that the Mud, found in the Nile, should come a far off; for then it would at last so raise the banks of this River, that it would not be able to overflow them any longer. Whereas 'tis more than 2000 years, that the banks thereof are not grown higher, there being now requisite but 16. cubits for overflowing the Land, no more than there was in the time of Herodotus. Which shews, saith he, that this Mud is nothing but a volatil Niter, which exhaling, doth not increase the Earth. As for the AEgyptian Dew, and the increase of the weight of the Mud, he adscribes them to the same Cause. For the spirits of Nitre abounding in the Nile, when raised into the Air with the vapors, that exhale continually from this River, there is made out of their mixture, a Dew, that refreshes the Air, makes sickness to cease, and produces all those admirable effects, that make the AEgyptians wish for it so passionately. And the same spirits of Niter, being joyned to the Paste, and to the Mud, raise the one, and augment the weight of the other. That, which Mr. Buratini observes, that at the time of this inundation, the Niter-pits of the neighboring places vomit out liquid Niter, and that one may see issue out of the Earth abundance of Chrystals of Nitre, is alledged to fortify this conjecture; Which is yet more confirm'd by the Fertility, communicated to the Earth by the Mud of this River. For, plants do grow there in such abundance, that they would choak one another, if it were not remedied by throwing Sand upon the Fields; insomuch that the AEgyptians must take as much pains to spread Sand to lessen the fatness of their Land, as other Nations do, to spread dung or other manure upon theirs to increase the fatness.
In the Fourth and Fifth, the Author undertakes to prove, that all those strange effects cannot be attributed to Rain or Snow, {253} and that the overflowing of the Nile always happens at a certain day.
In the Last, he alledges some Relations, serving to confirm his Opinion; Which are too long here to insist upon.
DE PRINCIPIIS ET RATIOCINATIONE GEOMETRARUM, Contra Fastum Professorum Geometriae; Authore Thoma Hobbes. It seems, that this Author is angry with all Geometricians, but himself; yea he plainly saith in the dedication of his Book, that he invades the whole Nation of them; and unwilling, it seems, to be call'd to an account for doing so; He will acknowledge no judge of this Age; but is full of hopes, that posterity will pronounce for him. Mean while he ventures to advance this Dilemma; Eorum qui de iisdem rebus mecum aliquid ediderunt, aut solus insanio Ego, aut solus non insanio; tertium enim non est, nisi (quod dicet forte aliquis) insaniamus omnes. Doubtless, one of these will be granted him.
As to the Book it self, he professes, that he doth not write it against Geometry, but Geometers; and that his design in it is, to shew, That there is no less uncertainty and falsity in the writings of Mathematicians, than there is in those of Naturalists, Moralists, &c., though he judges, that Physicks, Ethicks, Politicks, if they were well demonstrated, would be as certain as the Mathematicks.
Attacking the Mathematical Principles as they are found in Books, and withall some Demonstrations, he takes to task Euclid himself, instead of all, as the Master of all Geometricians, and with him his best interpreter, Clavius, examining in the First place, the Principles of Euclid: Secondly, Declaring false, what is superstructed upon them, whether by Euclid, or Clavius, or any Geometer whatsoever that hath made use of those or other (as he is pleased to entitle them) false Principles. Thirdly, Pretending, that he means so to combat all, both Principles and Demonstrations, undertaken by him, as that he will substitute better in their room, least he should seem to undermine the Science it selfe. {254}
The particulars, which he undertakes to reform, are,
Punctum. Linea. Terminus. Linea Recta. Superficies. Superficiei Termini. Superficies Plana, Angulus (Where he is large upon the Angulus Contactus.) Petitio prima Elem. 1. Euclidis. Ratio. Radix & Latus. Prop. 16. El. 3. Dimensio Circuli. Magnitudo Circuli Hugeniana. Sectio Anguli. Ratio, quam habet recta composita ex Radio & Tangente 30. grad, ad Radium ipsum. Propos. 47ae. Elem. 1. Demonstratio. Addita est Appendix de Mediis proportionalibus in genere.
KING SALOMONS POUTRAITURE OF OLD AGE; by John Smith, M.D. This Treatise being a Philosophical Discourse, though upon a Sacred Theme, may certainly claim a place among Philosophical Transactions. Not here to mention the many other learned Notes, this Worthy Author gives upon that Hieroglyphical Description of Old Age, made by that Royal Pen-man of Ecclesiastes, cap. 12. We shall onely take notice of that surprizingly Ingenious one, there to be met with, concerning the Antiquity of the Doctrine of the Blood's Circulation: King Salomon, who lived neer 2700 years agoe, using such expressions, as may, to a considering Reader, very probably denote the same Doctrine, which the Sagacious Dr. Harvey has of late years so happily brought to light, and introduced into all the most Ingenuous Societies of Learned men: The Pitcher, mention'd in the quoted place, being Interpreted for the Veines, and the Fountain for the Right Ventricle of the Heart, as the Cistern for the Left; the Wheele, there spoken off, manifestly importing a Circulation, made by the Great Artery with its Branches, the principal Instrument thereof.
* * * * *
Printed with Licence for John Martyn, and James Allestry, Printers to the Royal Society. 1666.
{255}
* * * * *
Num. 15.
PHILOSOPHICAL TRANSACTIONS.
* * * * *
Wednesday, July 18. 1666.
* * * * *
The Contents.
A new Experiment, shewing, How a considerable degree of Cold may be suddenly produced without the help of Snow, Ice, Haile, Wind, or Niter, and that at any time of the year. An Account of two Books, lately printed in London; whereof the one is entituled, EUCLIDIS ELEMENTA GEOMETRICA, novo ordine ac Methodo demonstrata; the Author Anonymus. The other, THE ENGLISH VINE-YARD VINDICATED, by JOHN ROSE.
* * * * *
A new Frigorifick Experiment shewing, how a considerable degree of Cold may be suddenly produced without the help of Snow, Ice, Haile, Wind, or Niter, and that at any time of the year.
This subject will it self, 'tis presumed, without any other Preamble, speak the Cause, why this present Paper is publish't at this (unusual) time of the Month: though, by the by, it may not be amiss to add on this occasion, that the Publisher of these Tracts never meant so to confine himself to a Set time, as not to retain the Liberty of taking any other, when there is occasion. And there being one given him, before another Month is come in, he does without any scruple or delay comply therewith, presenting the Curious with an Experiment which he thinks is both seasonable, and will not be unwellcome to them; furnish't out of the Ample Magazin of that Philosophical Benefactor, the Noble Mr. Boyle; Concerning which, thus much is further thought requisite to intimate on this occasion, that it, and some others of the same Gentlemans, that have been, and may be, mentioned in the Transactions, belong to certain Treatises, the Author hath lying by him; but that yet he denys not {256} to communicate them to his Friends, and to allow them to dispose thereof, upon a hope, that equitable Readers will be ready to excuse, if hereafter they should appear also in the Treatises they belong to, since he consents to this Anticipation, but to comply with those, that think the imparting of real and practical Experiments, may do the Publick some Service, by exciteing and assisting mens Curiosity in the interim.
As for the Experiment, you saw the other day at my Lodgings, though it belongs to some Papers about Cold, that (you know) could not be Publish't, when the rest of the History came forth, and therefore was reserved for the next Edition of that Book; yet the Weather having been of late very hot, and threatning to continue so, I presume, that to give you here in compliance with your Curiosity an Account of the Main and Practical part of the Experiment, may enable you to gratify not onely the Curious among your Friends, but those of the Delicate, that are content to purchase a Coolness of Drinks at a somewhat chargeable rate.
You may remember, that the Spring before the last, I shew'd you a particular Account of a way, wherein by a certain substance obtain'd from Sal Armoniack, I could presently produce a considerable degree of Cold, and that with odd Circumstances, without the help of Snow, Ice, Niter &c. But that Experiment being difficult and costly enough, and design'd to afford men Information, not Accomodations, I afterwards tryed, what some more cheap and facile mixtures of likely Bodies with Sal Armoniack would do towards the Production of Cold, and afterwards I began to consider, whether to that purpose alone (for my first experiment was design'd to exhibite other Phaenomena too) those mixtures might not without inconvenience be omitted: and I was much confirm'd in my conjecture, by an accident, which was casually related to me by a very Ingenious Physician of my acquaintance, but not to be repeated to you in few words, though he complain'd, he knew not what to make of it.
Among the several ways, by which I have made infrigidating Mixtures with Sal Armoniack, the most simple and facile is this; Take one pound of powder'd Sal Armoniack and about three Pints (or pounds) of Water, put the Salt into the Liquor, either altogether, if your design be to produce an intense, though {257} but a short coldness; or at two, three, or four several times, if you desire, that the produced coldness should rather last somewhat longer than be so great. Stirre the powder in the Liquor with a stick or whalebone (or some other thing that will not be injur'd by the fretting Brine, that will be made) to hasten the dissolution of the Salt; upon the quickness of which depends very much the intensity of the Cold, that will ensue upon this Experiment. For the clearing up whereof, I shall annex the following particulars.
[Sidenote: * In the History of Cold.]
1. That a considerable degree of Cold is really produced by this operation, is very evident: First to the touch; Secondly, by this, that if you make the Experiment (as for this reason I sometimes chuse to do) in a Glass-Body or a Tankard, you may observe, that, whilst the Solution of the Salt is making, the outside of the Metalline Vessel will, as high as the mixture reaches within, be bedew'd (if I may so speak) with a multitude of little Drops of Water as I have * elsewhere shown that it happens, when mixtures of Snow and Salt, being put into Glasses or other Vessels, the aqueous vapors that swim to and fro in the Air, and chance to glide along the sides of the Vessels, are by the coldness thereof condens'd into Water. And in our Armoniack Solution you may observe, that if you wipe off the Dew from any particular part of the outside of the Vessel, whilst the solution does yet vigorously goe on, it will quickly collect fresh Dew, which may be sometimes copious enough to run down the sides of the Vessel. But Thirdly, the best and surest way of finding out the Coldness of our Mixture is that, which I shew'd you by plunging into it a good seal'd Weatherglass furnish't with tincted Spirit of Wine. For the Ball of this being put into our frigorifick mixture, the Crimson Liquor will nimbly enough descend much lower, than when it was kept either in the open Air, in common Water, of the same temper with that, wherein the Sal Armoniack was put to dissolve. And if you remove the Glass out of our Mixture into common water, the tincted Spirit will, (as you may remember, it did) hastily enough reascend for a pretty while, according to the greater or lesser time, that it continued in the Armoniack Solution. And this has succeeded with me, when instead of removing the Mixture into Common Water, I removed it into water newly impregnated with Salt-peter.
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2. The Duration of the Cold, produc'd by this Experiment, depends upon several Circumstances; as First, upon the Season of the year, and present temperature of the Air; For, in Summer and Hot weather the Cold will sooner decay and expire. Secondly, upon the Quantity of Salt and Water: For, if both these be great, the effect will be as well more lasting, as more considerable. Thirdly, for ought I yet know, we may here add the Goodness & Fitness of the particular parcel of Salt, that is imploy'd; for, though it be hard to discern beforehand, which will be the more, and which the less proper; yet some trials have tempted me to suspect, that there may be a considerable disparity, as to their fitness to produce Cold, betwixt parcels of Salt, that are without scruple look't upon as Sal Armoniack: Of which difference it were not perhaps very difficult to asign probable reasons from the Nature of the Ingredients of this compound Concrete, and the wayes of preparing it. But the Duration of the Cold may be conceived to depend also. Fourthly, upon the Way of putting in the Salt into the Water. For, if you cast it in all at once, the Water will sooner acquire an intense degree of Coldness, but it will also the sooner return to its former temper; Whereas, if you desire but an inferiour degree of that Quality, but that may last longer (which wil usually be the most convenient for the Cooling of Drinks), then you may put in the Salt by little and little. For, keeping a long Weather-glass for a good while in our impregnated Mixture, I often purposely try'd, that, when the tincted liquor subsided but slowly, or was at a stand, by putting in, from time to time, 2 or 3. spoonfuls of fresh Salt, and stirring the Water to quicken the Dissolution, the Spirit of Wine would begin again to descend, if it were at a stand or rising, or subside much more swiftly than it did before. And if you would lengthen the Experiment, it may not be amiss, that part of the Sal Armoniack be but grosly beaten, that it may be the longer in dissolving, and consequently in Cooling the Water. Whilst there are dewy drops produced on the outside of the Vessel, 'tis a sign, that the Cold within continues pretty strong; for when it ceases, these drops especially in warm weather, will by degrees vanish. But a surer way of measuring the duration of the Cold, is, by removing from time to time the Seal'd Weather-glass out of the Saline Mixture into the same common Water, with part of which it was made. And though it be not easie to determin any thing particularly about this matter; yet it may somewhat assist you in your Estimates, to be inform'd, That I have in the Spring by a good Weather-glass found a sensible adventitious Cold made by a pound of Sal Armoniack at the utmost, to last about 2 or 3 hours.
3. To cool Drinks with this Mixture, you may put them in thin Glasses, the thinner the better; which (their orifices being stopp'd, and still kept above the Mixture) may be moved to and fro in it, and then be immediately pour'd out to be drunk: Though when in the Glass, I imployed, was conveniently shap'd as, like a Sugar-loaf, or with a long Neck, I found it not amiss to drink it out of that, without pouring it into any other; which can scarce be done without lessning the Coolness. The refrigeration, if the Glass viall be convenient, is quickly perform'd: And if one have a mind to cool his hands, he may readily do it by applying them to the outside of the Vessel, that contains the refrigerating Mixture; by whose help, pieces of Chrystal, or Bullet for the cooling of {259} the Mouths or Hands of those patients, to whom it may be allow'd, may be potently cool'd, and other such refreshments may be easily procur'd.
4. How far Sal Armoniack, mingl'd with Sand or Earth, and not dissolv'd, but only moistn'd with a little Water sprinkl'd on it, will keep Bottles of Wine or other liquors more coole, than the Earth or that Sand alone will do, I have not yet had opportunity by sufficient trials fully to satisfie my self, and therefore resign that Enquiry to the Curious.
5. For the cooling of Air, and Liquors, to adjust Weather-glasses (to be able to do which at all times of the year, was one of the chief aimes, that made me bethink my self of this Experiment;) or to give a small quantity of Beer &c. a moderate degree of coolness, it will not be requisite, to employ neer so much as a whole pound of Sal Armoniack at a time. For, you may easily observe by a seal'd Weather-glass, that a very few ounces, well pouder'd and nimbly dissolv'd in about 4. times the weight of Water, will serve well enough for many purposes.
6. And that you may the less, scruple at this, I shall tell you, that even before and after Midsummer, I have found the Cold producible by our Experiment to be considerable and useful for refrigerating of Drinks, &c. but if the Sal Armoniack be of the fittest sort (for I intimated above, that I suspected, 'tis not equally good) and if the season of the year do make no disadvantagious difference, the degree of Cold, that may be produced by no more than one pound (if not by less) of Sal Armoniack, may, within its own Sphere of Activity, be much more vehement, than, I presume, you yet imagine, and may afford us excellent Standards to adjust seal'd Weather glasses by; and for several other purposes, For I remember that in the Spring, about the end of March, or beginning of April, I was able with one pound of Sal Armoniack, and a requisite proportion of Water, to produce a degree of Cold much greater, than was necessary the preceding Winter, to make it frosty Weather abroad; nay I was able to produce real Ice in a space of time, almost incredibly short. To confirm which particulars, because they will probably seem strange to you, I will here annex the Transcript of an entry, that I find in a Note book of the Phaenomena and success of one of those Experiments, as I then tryed it; though I should be asham'd to expose to your perusal a thing so rudely pen'd; if I did not hope, you would consider, that 'twas hastily written onely for my own Remembrance. And that you may not stop at any thing in the immediately annext Note, or the two, that follow, it will be requisite to premise this Account of the seal'd Thermoscope; (which was a good one) wherewith these Observations were made; That the length of the Cylindrical pipe was 16. Inches; the Ball, about the bigness of a somewhat large Walnut, and the Cavity of the Pipe by guess about an eight or ninth part of an inch Diameter.
The First Experiment is thus registered. March the 27th, in the Seal'd Weather glass, when first put into the Water, the tincted Spirit rested at 8-5/8 inches; being suffered to stay there a good while, and now and then stirr'd to and fro in the Water; it descended at length a little beneath 7-5/8 inches; then the Sal Armoniack being put in, within about a quarter of an hour or a little more it descended to 2-11/16 inches, but before that time, in half a {260} quarter of an hour it began manifestly to freeze the vapours and drops of water on the outside of the Glass. And when the frigorifick power was arriv'd at the height, I several times found, that water, thinly plac'd on the outside, whilst the mixture within was nimbly stirr'd up and down, would freeze in a quarter of a minute (by a Minute-watch.) At about 3/4 of an hour after the infrigidating Body was put in, the Thermoscope, that had been taken out a while before, and yet was risen but to the lowest freezing mark, being again put in the liquor, fell an inch beneath the mark. At about 21/2 houres from the first Solution of the Salt I found the tincted liquor to be in the midst between the freezing marks, whereof the one was at 51/2 inches (at which height when the Tincture rested, it would usually be, some, though but a small, frost abroad;) and the other at 43/4 inches; which was the height, to which strong and durable Frosts had reduced the liquor in the Winter. At 3 hours after the beginning of the Operation, I found not the Crimson liquor higher than the upper Freezing mark newly mention'd; after which, it continued to rise very slowly for about an hour longer; beyond which time I had not occasion to observe it.
Thus far the Note-book; wherein there is mention made of a Circumstance of some former Experiments of the like kind, which I remember was very conspicuous in this newly recited. For, the frigorifick mixture having been made in a Glass body (as they call it) with a large and flattish bottom, a quantity of water, which I (purposely) spilt upon the Table, was by the operation of the mixture within the Glass, made to freeze, and that strongly enough, the bottom of the Cucurbite to the Table; that stagnant liquor being turn'd into solid ice, that continued a considerable while unthaw'd away, and was in some places about the thickness of a half Crown piece.
Another Observation, made the same Spring, but less solemn, as meant chiefly to shew the Duration of Cold in a high degree, is recorded in these terms: The first time, the Seal'd Weather-glass was put in, before it touch'd the common water, it stood at 8-1/8, having been left there a considerable while, and once or twice agitated the water, the tincted liquor sunk but to 7-7/8, or at furthest, 7-6/8; then the frigorifick liquor being put into the water with circumstances disadvantagious enough in (about) half a quarter of an hour the tincted liquor fell beneath 33/4, and the Thermoscope, being taken out, and then put in again, an hour after the water had been first infrigidated subsided beneath 5 inches, and consequently within 1/4 of an inch of the mark of the strongly freezing weather.
7. Whereas the grand thing, that is like to keep this Experiment from being as generally Useful, as perhaps it will prove Luciferous, is the Dearness of Sal Armoniack, two things may be offered to lessen this Inconvenience. For first, Sal Armoniack might be made much cheaper, if instead of fetching it beyond-sea, our Country-men made it here at home; (which it may easily be and I am ready to give you the Receipt, which is no great Secret.) But next, I considered, that probably the infrigidating vertue of our mixture might depend upon the peculiar Texture of the Sal Armoniack whereby, whilest the Water is dissolving it, either some Frigorifick particles are extricated and excited or (rather) some particles which did before more agitate the minute parts of the water, are expell'd (or invited out by the ambient Bodies) or {261} come to be clogg'd in their motion: Whence it seem'd reasonable to expect that upon the Reunion of the Saline particles into such a Body, as they had constituted before, the redintegrated Sal Armoniack having, neer upon, the same Texture, would, upon its being redissolv'd, produce the same, or a not much inferior degree of Coldness: And hereupon, though I well enough foresaw that an Armoniack solution, being boyl'd up in Earthen vessels (for Glass ones are too chargeable) would, by piercing them, both lose some of the more subtle parts, and thereby somewhat impaire the texture of the rest; yet I was not deceiv'd in Expecting, that the dry Salt, remaining in the pipkins, being redissolv'd in a due proportion of water, would very considerably infrigidate it; as may further appear by the Notes, which for your greater satisfaction you will find here subjoyn'd, as soon as I have told you, that, though for want of other vessels I was first reduc'd to make use of Earthen ones, and the rather, because some Metallin Vessels will be injur'd by the dissolv'd Sal Armoniack, if it be boyl'd in them; yet I afterwards found some conveniencies in Vessels of other Mettall, as of Iron; whereof you may command a further Account.
March the 29th, the Thermoscope in the Air was at 8-7/8 inches; being put into a somewhat large evaporating glass, fill'd with water, it fell (after it staid a pretty while, and had been agitated in the liquor) to 8. inches: then about half the Salt, or less, that had been used twice before, and felt much less cold than the water, being put in and stirr'd about, the tincted Spirit subsided with a visible progress, till it was faln manifestly beneath 4. inches; and then, having caused some water to be freshly pump'd and brought in; though the newly mention'd Solution were mixt with it, yet it presently made the Spirit of Wine manifestly to ascend in the Instrument, much faster, than one would have expected, &c.
And this much may suffice for this time concerning our Frigorifick Experiment; which I scarce doubt but the Cartesians will lay hold on as very favourable to some of their Tenents; which you will easily believe, it is not to the Opinion, I have elsewhere oppos'd, of those Modern Philosophers, that would have Salt-petre to be the Primum Frigidum: (though I found by trial, that, whilst 'tis actually dissolving, it gives a much considerabler degree of Cold, than otherwise.) But about the Reflexions, that may be made on this Experiment, and the Variations, and Improvements & Uses of it, though I have divers things lying by me; yet, since you have seen several of them already, and may command a sight of the rest, I shall forbear the mention of them here, not thinking it proper, to swell the bulk of this Letter with them.
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An Account of two Books lately printed in London.
I. EUCLIDIS ELEMENTA GEOMETRICA, novo ordine ac methodo demonstrata. In this compendious and pretty Edition, the Anonymous Author pretends to have rendred these Elements more expeditious; by bringing all together into one place, what belongs to one and the same subject: Comprising 1. what Euclid hath said of Lines, Streight, Intersecting one another, and Parallel. 2. What he hath demonstrated of a Single Triangle, and of Triangles Compared one with another. 3. What of the Circle, and its Properties. 4. What of Proportions in Triangles and other Figures. 5. What of Quadrats and Rectangles, made of Lines diversly {262} cut. 6. What of Plane Superficies's. 7. What of Solids. After which follow the Problems. The Definitions are put to each Chapter as need requireth. The Axioms, because they are few, and almost every where necessary, are not thus distributed in Chapters. The Postulata, are not subjoyn'd to the Axioms, but reserv'd for the Problems, the Author esteeming, that they being practical Principles, had only place in Problems.
This for the Order: As to the Manner of Demonstrating, One and the same is observ'd in most Propositions; all with much brevity; to the end, that what is not of it self difficult, may not be made so, by multitude of Words and Letters.
II. THE ENGLISH VINE-YARD VINDICATED. The Author (Mr. John Rose, his Majesties Gardener at his Royal Garden in St. James's) makes it his business in this small Tract (a very thin Pocket-book) by a few short Observations made by himself, to direct Englishmen in the Choice of the Fruit, and the Planting of Vine-yards; heretofore very frequently cultivated, though of late almost quite neglected by them.
He discourses skilfully, 1. Of the severall sorts of Vines, and what Grapes are most sutable to the Climate of England; where he chiefly commends the small Black-grape, or Cluster-grape; the Parsley-grape; the White Muscadine; the Frontiniack; and a new White-grape, with a red Wood and a dark green Leaf: All these being early ripe fruit. 2. Of the Soyle, and Scituation of a Vine-yard in England: Where, as to the First, he pitches upon a Light Soile, having a bottom of Chalk or Gravel, and given to Brambles observing, that no Plant whatsoever is so connatural to the Vine for Soyl, as the Bramble. As for the Scituation he chooses that side or declivity of a Hill, that lies to the South or Southwest; and is favoured with other Hills somewhat higher, or Woods on the North and East, to break the rigour of those quarters. This direction he thinks of that importance, that he affirms, that the discouragement of the Culture of Vines in England has only proceeded from men's misinformation on this material article of Choice of Soyle and Scituation. 3. How to prepare the Ground for the Plantation, vid. by plowing up the Swarth in July, and by disposing the Turf in small heaps, and so burning them, and spreading the ashes over the Land; care being taken, that by heaping too much materials together, the Earth be not over-burnt by the excessive heat and fire, which they require to reduce them to ashes.
What is added, of the Manner of planting the Sets; of Dressing, Pruning, and Governing the Plantation; of the Ordering and Cultivating the Vine-yard after the first four years, till it needs renewing; as also of the manner and time, how and when to manure the Vine-yard, with Compost, will be better understood from the Book it self, than can be here described; the Author pretending, that, those few observations of his, as the native production of his own Experience, being practised with care, the Vine-yards in England may be planted, govern'd and perpetuated with undoubted success; and offering withall to furnish those, that have a desire to renew this Culture, and to store their grounds with Sets and Plants of all those sorts, which he recommends; he having a plentiful stock of them all.
* * * * *
Printed with Licence for John Martyn, and James Allestry, Printers to the Royal Society. 1666.
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Num. 16.
PHILOSOPHICAL TRANSACTIONS.
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Munday, August 6. 1666.
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The Contents.
An essay of Dr. John Wallis, exhibiting his Hypothesis about the Flux and Reflux of the Sea, taken from the consideration of the Common Center of Gravity of the Earth and Moon; together with an Appendix of the same, containing an Answer to some Objections, made by severall Persons against that Hypothesis. Some Animadversions of the same Author upon Master Hobs's late Book, De Principiis & Ratiocinatione Geometrarum.
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An Essay of Dr. John Wallis, exhibiting his Hypothesis about the Flux and Reflux of the Sea.
How abstruse a subject in Philosophy, the Flux and Reflux of the Sea hath proved hitherto, and how much the same hath in all Ages perplexed the Minds even of the best of Naturalists, when they have attempted to render an Account of the Cause thereof, is needless here to represent. It may perhaps be to more purpose, to take notice, that all the deficiencies, found in the Theories or Hypotheses, formerly invented for that End, have not been able to deterre the Ingenious of this Age from making farther search into that Matter: Among whom that Eminent Mathematician Dr. John Wallis, following his happy Genius for advancing reall Philosophy, hath made it a part of his later Inquiries and Studies, to contrive and deduce a certain Hypothesis concerning that Phaenomenon, taken {264} from the Consideration of the Common Center of Gravity of the Earth and Moon, This being by several Learned Men lookt upon, as a very rational Notion, it was thought fit to offer it by the Press to the Publick, that other Intelligent Persons also might the more conveniently and at their leisure examine the Conjecture (the Author, such is his Modesty, presenting it no otherwise) and thereupon give in their sense, and what Difficulties may occur to them about it, that so it may be either confirm'd or laid aside accordingly; As the Proposer himself expressly desires in the Discourse, we now, without any more Preamble, are going to subjoyn, as it was by him addressed, by way of Letter, from Oxford to Mr. Boyle, April 25. 1666. and afterwards communicated to the R. Society, as follows:
You were earnest with me, when you last went from hence, that I would put in writing somewhat of that, which at divers times, these three or four years last past, I have been discoursing with your self and others concerning the Common Center of Gravity of the Earth and Moon, in order to salving the Phaenomena as well of the Seas Ebbing and Flowing; as of some perplexities in Astronomical Observations of the Places of the Celestial Bodies.
How much the World, and the great Bodies therein, are manag'd according to the Laws of Motion, and Statick Principles, and with how much more of clearness and satisfaction, many of the more abstruse Phaenomena have been salved on such Principles, within this last Century of years, than formerly they had been; I need not discourse to you, who are well versed in it. For, since that Galilaeo and (after him) Torricellio, and others, have applied Mechanick Principles to the salving of Philosophical Difficulties; Natural Philosophy is well known to have been rendered more intelligible, and to have made a much greater progress in less than an hundred years, than before for many ages.
The Seas Ebbing and Flowing, hath so great a connexion with the Moons motion, that in a manner all Philosophers (whatever other Causes they have joyned with it), have attributed much of its cause to the Moon, which either by some occult quality, {265} or particular influence, which it hath on moyst Bodies, or by some Magnetick vertue, drawing the water towards it, (which should therefore make the Water there highest, where the Moon is vertical) or by its gravity and pressure downwards upon the Terraqueous Globe (which would make it lowest where the Moon is vertical) or by whatever other means (according to the several Conjectures of inquisitive persons,) hath so great an influence on, or at least a connexion with, the Sea's Flux and Reflux, that it would seem very unreasonable, to seclude the consideration of the Moons motion from that of the Sea: The Periods of Tides (to say nothing of the greatness of them near the New moon and Full moon) so constantly waiting on the Moon's motion, that it may be well presumed, that either the one is governed by the other, or at least both from some common cause.
But the first that I know of, who took in the consideration of the Earth's motion, (Diurnal and Annual) was Galilaeo; who in his Systeme of the World, hath a particular discourse on this subject: Which, from the first time I ever read it, seemed to me so very rational, that I could never be of other opinion, but that the true Account of this great Phaenomenon was to be referred to the Earths motion, as the Principal cause of it: Yet that of the Moon (for the reasons above mentioned) not to be excluded, as to the determining the Periods of Tides, and other circumstances concerning them. And though it be manifest enough, that Galilaeo, as to some particulars, was mistaken in the account which there he gives of it; yet that may be very well allowed, without any blemish to so deserving a person, or prejudice to the main Hypothesis: For that Discourse is to be looked upon onely as an Essay of the general Hypothesis; which as to particulars was to afterwards adjusted, from a good General History of Tides; which it's manifest enough that he had not; and which is in a great measure yet wanting. For were the matter of Fact well agreed on, it is not likely, that several Hypotheses should so far differ, as that one should make the Water then and there at the Highest, where and when the other makes it at the Lowest; as when the Moon is Vertical to the place. {266}
And what I say of Galilaeo, I must in like manner desire to be understood of what I am now ready to say to you. For I do not profess to be so well skilled in the History of Tides, as that I will undertake presently to accommodate my general Hypothesis to the particular cases; or that I will indeed undertake for the certainty of it, but onely as an Essay propose it to further consideration; to stand or fall, as it shall be found to answer matter of Fact. And truly had not your importunity (which is to me a great Command) required me to do it, I should not so easily have drawn up any thing about it, till I had first satisfied my selfe, how well the Hypothesis would answer Observation: Having for divers years neglected to do it, waiting a time when I might be at leisure throughly to prosecute this design.
But there be two reasons, by which you have prevailed with me, at least to do something. First, because it is the common Fate of the English, that out of a modesty, they forbear to publish their Discoveries, till prosecuted to some good degree of certainty and perfection; yet are not so wary, but that they discourse of them freely enough to one another, and even to Strangers upon occasion; whereby others, who are more hasty and venturous, comming to hear of the notion, presently publish something of it, and would be reputed thereupon, to be the first Inventers thereof: though even that little, which they can then say of it, be perhaps much less, and more imperfect, than what the true Authors could have published long before, and what they had really made known (publikely enough, though not in print) to many others. As is well known amongst us as to the business of the Lymphatick Vessels in Anatomy; the Injection of Liquors into the veins of Living animals; the Exhibiting of a straight line equal to a crooked; the spot in Jupiter, whence his motion about his own Axis may be demonstrated; and many other the like considerable Inventions.
The other Reason (which, with me, is more really of weight, though even the former be not cotemptible) is, because, as I have been already for at least three or four years last past diverted from prosecuting the inquiry or perfecting the Hypothesis, as I had thoughts to do; so I do not know, but like Emergencies may divert me longer; and whether I shall ever so {267} do it, as to bring it to perfection, I cannot determine. And therefore, if as to my self any thing should humanitus accidere; yet possibly the notion may prove worth the preserving to be prosecuted by others, if I do it not. And therefore I shall, at least to your self, give some general account of my present imperfect and undigested thoughts.
I consider therefore, that in the Tides, or the Flux and Reflux of the Sea, besides extraordinary Extravagancies or Irregularities, whence great Inundations or strangly high Tides do follow, (which yet perhaps may prove not to be so meerly accidental as they have been thought to be, but might from the regular Laws of Motion, if well considered, be both well accounted for and even foretold;) There are these three notorious Observations made of the Reciprocation of Tides. First, the Diurnal Reciprocation; whereby twice in somewhat more than 24. hours, we have a Floud and an Ebbe; or a High-water and Low-water. Secondly, the Menstrual; whereby in one Synodical period of the Moon, suppose from Full-moon to Full-moon, the Time of those Diurnal Vicissitudes doth move round through the whole compass of the [Greek: Nuchthemeron], or Natural day of twenty four hours: As for instance, if at the Full-moon the full Sea be at such or such a place just at Noon, it shall be the next day (at the same place) somewhat before One of the clock; the day following, between One and Two; and so onward, till at the New moon it shall be at midnight; (the other Tide, which in the Full moon was at midnight, now at the New-moon coming to be at noon;) And so forward till at the next Full-moon, the Full sea shall (at the same place) come to be at Noon again: Again, That of the Spring-tides and Neap-tides (as they are called;) about the Full-moon and New-moon the Tides are at the Highest, at the Quadratures the Tides are at the Lowest: And at the times intermediate, proportionably. Thirdly, the Annual; whereby it is observed, that at sometimes of the year, the Spring-tides are yet much higher than the Spring-tides at other times of the year: Which Times are usually taken to be at the Spring and Autumne; or the two AEquinoxes; but I have reason to believe (as well from my own Observations, for many years, as of others who have been {268} much concerned to heed it, whereof more will be said by and by;) that we should rather assign the beginnings of February and November, than the two AEquinoxes. |
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