It may be further observed that a frost of this kind is very limited in its duration, seldom lasting more than thirty-six or forty hours. On the morning of the second day after its commencement, a visible relaxation takes place in the temperature of the atmosphere. Usually before noon, the wind on a sudden shifts to the south-west, and a rapid thaw comes on, frequently attended with rain. What appears somewhat remarkable is, that during several hours after the commencement of the thaw, the production of ice at the bottom of rivers seems to go on without abatement, and upon examining a rapid stream, the stones over which it flows will be found at this period completely incrusted with the above description of icy plates. It seems evident from this that the bed of the river, which has been reduced below the freezing temperature, is not for some time affected by the change of the atmosphere. This may be in some measure illustrated by the well-known fact, that rain which falls upon a rock or stone wall, is frequently converted into ice, though the air and the ground are evidently in a state of thaw. Before the following morning, the ice of which we have been speaking generally disappears, being carried away by the current or dissolved by the thaw.

The last time that I remarked this phenomenon, was in a stream of the river Aire, near Bradford, in Yorkshire, on the 1st of January, 1814. This instance did not precisely accord with what I have stated to be the usual circumstances of the case, as the frost then had existed several days without any previous appearance of this kind; but there were several indications of approaching change of temperature, and the day following there was a partial thaw attended with rain, the wind having veered from north-west to south-west. This thaw, however, did not continue long, and was succeeded by a frost which surpassed all within my recollection in severity and duration. Yet during the whole of the period, though the thermometer often stood below 18 degrees Fahrenheit, and the estuary of the Tees several miles below Stockton, where the spring-tides rise from twelve to eighteen feet, was for two months frozen over, so as to allow the passage of a loaded waggon, I could never perceive a particle of ice adhering to the rock or gravel, in the bed of the small and rapid river Leven in Cleveland, where I then resided. This circumstance seems decisively to prove that the phenomenon does not merely depend on an intensity of cold.

I confess I am unable to frame any hypotheses respecting the above-mentioned facts which would not be liable to numerous and formidable objections. The immediate cause of the formation of the ice seems to be a rapid diminution of the temperature in the stone or gravel in the bed of the river, connected with the sudden changes in the state of the atmosphere, but it does not seem very easy to explain the precise nature of this connection.

We may easily conceive that by a sudden change from a state of thaw to an intense frost attended by a strong wind, the whole body of water in a river may become quickly cooled, and consequently diminish the temperature of the stone or gravel over which it flows; but to suppose that water which is not itself at freezing- point is capable of reducing the substances in contact with it by means of a continual application of successive particles so far beneath that temperature as in process of time to convert the contiguous water to ice, seems not to accord very well with the usually received theory of the equilibrium of caloric. However, the fact that the quantity of ice thus produced is always greater in proportion to the superior velocity of the stream, little or none being found where there is no sensible current, seems in some degree to countenance the above idea.

I cannot learn that any experiments have ever been instituted on this subject, though it seems that they might easily be made by a person conveniently situated and possessed of the necessary instruments. A careful examination by properly contrived thermometers of the relative temperatures of the air, the water, and the bed of the river and of the changes undergone by them during the above process, would probably go a great way towards solving the problem. I know no one better qualified for this undertaking than Mr. Knight, if he should at any future time have leisure and opportunity to direct towards it the same acuteness of observation and accuracy of investigation which have enabled him to make such important discoveries in the economy of the vegetable kingdom, and if the explanation of this phenomenon should ever lead to results of any importance to the cause of science, I shall feel sufficiently satisfied if it be deemed that I have been of any service in pointing out the way.

RICHARD GARNETT.

BLACKBURN, May 16th, 1818.

* * * * *

GOSSAMER.

CLITHEROE, October 20th, 1859.

To the Editor of the "Field."

"A Young Inquirer" asks what is the cause of that appearance so often met with in the autumn, resembling spider-webs. He says, if it be the production of that insect, how do you account for their hanging apparently unsuspended in the air, as it is seen fifty or sixty feet high, without a tree or any other object near to which it could be attached?

I suppose you have not time to give to such questions minutely, as your reply would lead one to infer that Gossamer proceeded from spiders in general; and if it be meant that all true spiders spin, it is no doubt correct; but the Gossamer which "A Young Inquirer" asks about is the production of a small black spider about the size of a flea, which was a true aeronaut long before Montgolfier or Lunardi, and if "A Young Inquirer" has access to either the "Linnean Transactions" or the first series of Loudon's "Magazine of Natural History," he will find particulars in the latter, showing that a violent controversy raged through the three first volumes between Mr. Blackwall and Dr. Murray on the question whether the ascent of this spider (A. AEronautica) was electric, or whether it merely travelled in the direction of the wind. But if "A Young Inquirer" would deserve his name, let him begin with these spiders and observe for himself; he will find the inquiry highly interesting.

He has no doubt frequently seen a small black spider creeping on his hat or clothes (if he lives in the country this must have occurred to him many times); this is the aeronautic spider. Let him take this upon his hand, and if he be in the house let him carry it to the open door or window, and allow it to creep up to the tip of his finger, which he must then hold in a horizontal position. When the spider finds it can proceed no further by creeping, it generally drops a few inches, where it remains suspended for a short time, apparently quite still, but if very closely observed another thread (Gossamer) may be seen proceeding from its vent, and when this has reached the length which the spider's instinct tells it is sufficient for the purpose, it cuts off the connection till then existing between it and the thread by which it has hitherto been suspended from the finger, and floats away into space. Very often it rises almost vertically, sometimes its course is nearly horizontal, and sometimes it is oblique.

I cannot say, as Mr. Murray does, that I have seen the spider go against the wind, neither can I confirm Mr. Blackwall's assertions that he always goes right before the wind, for I have seen him go apparently across the current, so far as I could judge of the direction of the wind at the time.

If "A Young Inquirer" makes the experiment I have suggested, let him not be discouraged if the first he tries does not go off at all, as I have sometimes found this to be the case, which I accounted for by supposing that possibly the supply of materials might be exhausted at the time.

I do not remember that I ever saw one of these aeronautic spiders preying upon any insect, yet it must be for some such purpose that they ascend to great altitudes, sometimes in countless numbers, and the way they come down again is quite as curious as the manner in which they ascend.

Many years since, as I was walking over the hills in the neighbourhood of Blackburn, on a bright, still morning in September, thousands of small locks of what looked like cotton wool were slowly descending to the ground from various altitudes— some as high as I could see—and tens of thousands of similar locks were lying on the ground on both sides of the path by which I was travelling; and on examination I found that all these locks were Gossamer, some with the spider still with them, but generally deserted. The spiders when they wanted to come down, finding there was no descending current of air, or perhaps, as Mr. Murray says, no electricity, determined to descend in parachutes; they therefore had drawn up their cables hand over hand (as they may often be seen to do when they wish to ascend their own lines) until they accumulated a mass heavy enough to fall by its own weight, and carry them along with it.

I have seen Gossamer in this form at other times before and since, but in the likeness of a snow-shower I never saw it except on that occasion, and, if I recollect aright, the same enormous shower of Gossamer was observed to extend as far as Liverpool.

What induced these millions of spiders to go up at the same time, of course I do not know, and can only suppose that they went up to feed; but, as I have said previously, I never saw one of this species preying upon anything. The idea that they go aloft to kill the Furia Infernalis is too fanciful to deserve credit. Who knows whether the Furia Infernalis is anything else than a murderous Mrs. Harris—at all events, who has seen one, and what was it like?

I suppose they are true sportsmen, and disdaining to take their fish in nets, they, like thorough brothers of the angle, fish only with fine gut.

Gilbert White noticed one of these showers of Gossamer, and as his account is very interesting, I quote it. He says that on the 21st of September, 1741, intent upon field diversions, he rose before daybreak, but on going out he found the whole face of the country covered with a thick coat of cobweb drenched with dew, as if two or three setting-nets had been drawn one over the other. When his dogs attempted to hunt, their eyes were blinded and hoodwinked, so much that they were obliged to lie down and scrape themselves. This appearance was followed by a most lovely day. About 9 A.M. a shower of these webs (formed not of single threads, but of perfect flakes, some near an inch broad and five or six long) was observed falling from very elevated regions, which continued without interruption during the whole of the day, and they fell with a velocity which showed they were considerably heavier than the atmosphere. When the most elevated station in the country where this was observed was ascended, the webs were still to be seen descending from above, and twinkling like stars in the sun, so as to draw the attention of the most incurious. The flakes of the web on this occasion hung so thick upon the hedges and trees, that basketsful might have been collected. No one doubts (he observes) but that these webs are the production of small spiders.

These aerial spiders are of two sizes, although of the same colour and general appearance; they are probably male and female. At all events they do not vary in size more than other species of spiders when the sexes differ.

Has it been observed by naturalists that spiders eat their own webs? A large one that I used to feed when I was a lad with wasps, humble bees, and flesh-flies, used to do so occasionally. These insects were so strong that they often ruined the web in their efforts to escape, and the spider, quite aware of the rough customers it had to deal with, would often coil a cable of many folds round them before venturing to seize them with its mandibles. It would, if the web was ruined by the struggles of the insect, deliberately gorge it, which I accounted for by supposing that unless it did so it would not be able to secrete a sufficient supply of material to enable it to spin another.

The leaping spiders are another curious species, which construct no webs, although they spin threads. This spider may be seen frequently on the walls of houses, and if carefully watched it will be seen to range up and down in quest of small gnats and other insects; when it observes one it creeps to within about two inches of it, and backing slightly, it appears to hesitate for a moment, and then springs upon the fly, but always before doing so it fixes a thread to the spot from whence it springs, so that if the fly happens to be too strong for it, and is able to detach itself from the wall, they both remain suspended from the thread which has been previously fixed by the spider. This I have seen more than once.

They sometimes venture on larger game than the small gnats. One I was watching one day came upon one of the large Ephemera (the Browndrake), an insect ten times as large as the spider, but after many points (for the setting of the spider before it springs is very similar in manner to that of a thoroughbred pointer [17]), in which it kept varying its position, apparently to gain some advantage, it gave up the attempt, discretion proving the better part of valour.

When botanizing on Erris Begh (in Connemara), this summer, I passed through many spider-lines so strong as to offer a very sensible resistance before breaking. I don't remember to have ever before met with them so strong and tenacious, and the makers of optical instruments might there have found abundance of threads which I am told are valuable as cross-wires for transit- instruments and theodolites. I did not meet with any of the spiders that had thrown out these lines, but judging of them by their works I suppose they must have been large ones.

One of your correspondents was inquiring a few weeks since how it was that a spider could throw out a long line between two trees or buildings at a considerable distance from each other. This seems to me to be very easily explained, if we reason from the analogy of the flying spider. The spider seems to throw out a line, trusting it will catch somewhere or other, and it is able to ascertain it has done so by pulling at it, and when it finds that it is firmly fixed it starts off to travel upon it, as I have occasionally noticed.

Everyone has noticed how carefully the spider carries her cocoon of eggs attached to the vent, and how disconsolate she appears to be when deprived of them; but I don't think it is so generally known that some of the spiders carry their young on their backs for some time after they are hatched. I remember seeing an instance of this one day when on the Moors, grouse-shooting. I saw what seemed to be a very curious insect travelling on the ling (heather), and on stooping down to examine it I found it was a large spider, upon the back of which (in fact, all over it) were clustered some dozens of young ones, about the size of pins' heads; she also seemed to guard them with great care, and seemed much afraid of losing them.

FINIS.

NOTES.

[1] There is a fish somewhat resembling the Brambling in the Dunsop, a tributary of the Hodder, where it is known by the name of the Bull Penk.

[2] My opinion that neither Trout nor Salmon spawn every year is I think strongly corroborated by the fact, that previous to the Act of 1861 the London fish market was supplied with Salmon of the largest size, and of the best quality, in October, November, and December. When these fish were examined, it was found that the ovaries were but small, and the individual ova were not larger than mustard seed. These fish could not have spawned that season, nor would they have done so if left alive, if the growth of the ova in the ovaries is uniform—I mean if the growth of the ova is as great in one month as another—because in May and June the ova in a female Salmon is four times as large as these were in November.

Again, when the gas tank at Settle was emptied into the Ribble, in September, 1861, all the fish so far as was known were killed between that place and Mitton, Salmon as well as Par and Trout. Supposing that Salmon spawn every year, and that the Smolts come up the river, as Grilse in the summer of the same year in which they have gone to the sea in the spring, there ought to have been a great scarcity of both Grilse and Salmon in the Ribble in the year 1862, but so far was this from being the case, that both Grilse and Salmon were more abundant that season than they had been for some years previously, but there was a scarcity of both in 1863.

Again, when the Smolts were turned out of the breeding ponds at Dohulla, Galway, the experiment was looked upon as a failure because no Grilse returned the same season, not one having showed itself, but many came the summer after, proving pretty conclusively that in some rivers, at all events, the Smolt requires a year's residence in the sea before it returns as Grilse.

[3] In the evidence of Mr. George Hogarth, it is stated that he saw upwards of ninety Kelt fish in the mill lead at Grandholme, on the Don, May 6th.

[4] Salmon are said to produce 18,000 or 20,000 eggs each, and I have no doubt that a large Salmon will produce more, as one I examined a year or two ago, of about ten pounds weight, had a roe which weighed two pounds nine ounces, and the skin in which the eggs were enveloped (they were not in the loose state in which they are found just before exclusion) weighed three ounces, after all the eggs were washed from it; so that there were thirty-eight ounces of eggs. I weighed fifty of them, and found they weighed sixty-five grains. At that rate, thirty-eight ounces would give 12,788, and 300 lbs. 1,615,000; but as they would be much lighter when dried and potted than when taken from the belly of the fish, we may safely estimate that the 300 lbs. would contain 2,000,000, a prodigious number to pass through the hands of one tackle maker in a season.

[5] From "Loudon's Magazine of Natural History."

[6] I have frequently found, when catching Trout for this purpose, that the milt and roe were not ready for exclusion; when this was the case, I put them into a wire cage, which I sunk in the water, examining the fish every week, until I found they were in a fit state for the experiment.

[7] I fancy that if the ova come in contact with the air on exclusion, they are not so readily impregnated as if they are always covered with the water, and therefore I have laid some stress on the desirableness of keeping the air excluded from the ova as much as possible.

[8] There is, however, one fact which must lead a casual observer to suppose that the ova are impregnated twelve months before exclusion. It is this: the male Par (Salmon fry) are at this season, October, full of milt, almost ready for exclusion; whilst, in the female, the ova are so small that they require a microscope to see them individually, and the whole ovary is merely like a thread, leading to the conclusion that either the milt of the male is not required for the female Par, or the ova are impregnated twelve months before exclusion. The fact is, that the milt of the Par is used to impregnate the ova of the Salmon on the spawning beds.

[9] When I commenced this paper I had no doubt that hybrids had been produced between the Sprod (sea Trout) and the common Trout; since then, having seen the fry said to be so produced, and on making some further inquiries, I find there is some doubt whether the female was a Sprod, or merely a white Trout, and therefore I cannot confidently assert (as some time ago I believed I could) that hybrid fish had already been produced. As some of my readers may not know what a Sprod is, it may be necessary to explain. In the Ribble we have a fish ascending from the sea in July and August, weighing from six to ten ounces, which, in appearance at least, is a miniature Salmon. I believe the same fish is called a Whitling in Scotland. Besides this, we have a similar but larger fish, which begins to come a little earlier, and which weighs from one to three pounds; this, in the Ribble, is called a Mort (in Scotland a sea Trout). Both these fish (if they are two species) afford splendid sport to the angler, who must never consider them beaten until he has them in the landing-net. They are also delicate eating.

Note on cross-breeding of Fish.

Since the above paper was published, the breeding of Hybrids has been successfully accomplished. I have had fish sent from two different gentlemen living on the banks of the reservoirs belonging to the Liverpool Waterworks; these were beautiful fish (three in number), more like the sea Trout than the Salmon, and the largest of them weighing two pounds. I had put them into the brooks running into the reservoirs three years before.

I also learn from a friend that a beautiful specimen of the ombre Chevalier (French Char) was taken out of the Rivington reservoir. About a thousand had been put there by me two years before.

[10] Persons conversant with the habits of birds will readily comprehend me; for the sake of those who do not, I will just observe that the flight of all the Wagtails is very peculiar, being a succession of great leaps in the air (if I may be allowed the expression), which form a series of curves, the bird rising considerably at the commencement of each effort, and sinking again at the close.

[11] The intrepid and unfortunate traveller Joseph Ritchie, who accompanied Captain Lyon's expedition to Fezzan, and died there in 1819. Mr. Ritchie was a native of Otley, and an intimate friend of Mr. Garnett and his brothers. The beautiful poem from which the quotation is taken is printed in Alaric Watts's "Poetical Album."

[12] 1853.—I regret that in 1853, and for some years previous, we have not seen one. I fear they are extinct. The smaller kind are still numerous.

[13] The male Par is an exception to this rule.

[14] It appears to be a beautiful provision of Nature that mixture with water should increase the sphere of its action. Spallanzani found by actual experiment that three grains of the seed of a male frog might be diluted with a pint of water without destroying its stimulating power. See "Dissertations," vol. ii. p. 142, chap. 3, Ed. "Mag. Nat. History."

[15] Mr. Thomson, of Primrose.

[16] Assistant Keeper of Printed Books in the British Museum. Author of "Philological Essays," &c.

[17] The toad, when going to take a bee, points for a second or two as beautifully as the best-trained pointer before it strikes with its tongue.

THE END