on the remaining part of the joint next the body, which, as a natural styptic, instantly stops the bleeding, and gradually hardens and grows callous, and forms into a leg in miniature, which by degrees shoots forth, and attains to its natural size, to supply the place of that which was lost.

The crabs are naturally very quarrelsome, and with their great legs or claws fight and kill each other: with them they catch hold of their adversary's legs, and whatever they seize, they strongly retain for a long while: there is no escaping their cruel foe, but by voluntarily leaving a part of the leg behind, in token of victory; but the principal end for which this is done, is the saving the life of the conquered; for when they are bitten and bruised, and cannot break off that limb, they soon bleed to death.

The fishermen showed an experiment, to give some idea of the tenacious disposition of this creature, by obliging a crab with its great claw to lay hold of a small one; the silly creature did not distinguish that itself was the aggressor; but exerted its strength, and soon cracked the shell of its own small leg, and it bled freely; but feeling itself wounded, to save its life required a power peculiar to itself to break off that limb in the usual place; which it presently effected, and held fast for a long time the broken part in his great claw: which evidently shows, that this creature retains whatever it lays hold on, and when overcome by its enemy, ransoms its life at the expense of a limb.

Observations on the Precipices or Cliffs on the North-east Sea Coast of the County of Norfolk. By Mr. WILLIAM ARDERON.[1746.]

THE various strata, which make up this long chain of mountainous cliffs, must be very interesting to every one, who takes a pleasure in looking into the many changes which the earth undoubtedly has undergone, since its first creation. Vegetable mould, sands of various kinds and colours, clays, loams, flints, marls, chalk, pebbles, &c., are here to be seen at one view beautifully interspersed; and frequently the same kind many times repeated; as if at one time dry land had been the surface; then the sea; after, morassy ground; then the sea, and so on, till these cliffs were raised to the height they are now found.

This is demonstrated by the roots and trunks of trees, which are to be seen at low water in several places on this coast

near Hasborough and Walket: bones of animals are often found here also.

These hills seem to have been formerly the boundaries to an arm of the sea, which made Norwich a famous sea-port. This some of our ancient histories make mention of as an undoubted truth, though now considered as a mere fable, as no vestiges of it remain above ground at this day.

In the above-mentioned marl pits he discovered a stratum of shells, of about two feet thick, running nearly parallel to the horizon. He examined carefully this stratum, where he found a great many kinds of shells; but none which had withstood time's all-devouring teeth, so as to bear the handling; excepting the common wilk, some of which were very perfect. Among the variety of things he noticed in this stratum was a piece of coal, which he picked out from among the shells. This must have lain here as long as they, and been brought from some other county, as nothing of its kind is to be found here, but what is brought from distant parts. These shells lie 14 yards above the surface of the river, and nearly six beneath the top of the hill, and he believes 34 yards above the surface of the sea at Yarmouth. And it is very remarkable, that in these marl pits, six or seven yards lower than the above-mentioned stratum of shells, are found a vast quantity of stags' horns lying in all directions. Several I took out with my own hands; and the workmen, who are employed here, say, that they scarcely work a day, but they find more or less of them. But none are found entire.

These horns have been very large ones; some of the spines measuring 12 inches and upwards in length. Many of them are more than 2 inches in diameter, and several of them above 12 inches from spine to spine.

Another curiosity was the entire skeleton of a man, which was found in the same stratum with the above-mentioned horns, as one of the workmen assured me: he said, he took the pains to lay it altogether on the grass, as regularly as he was able; but his curiosity being then satisfied, he left it to be ground to pieces by the carts and waggons that came thither for the marl.

Among the clay lie a great many knots, lumps, or nodules, of a bluer kind of earth, not widely differing from that which is found in Harwich cliff: these, when digged up, are soft; but when they have been for some time exposed to the open air, they become almost as hard as flint. In and upon these lumps are the impressions of the cornu ammonis, or snakestones, in a beautiful manner, from one inch to five or six in

diameter, and several have part of the shells on them, of a yellowish white. Many other shells are found in these lumps; as the pectunculus, helmet stones, belemnites, common cockle, turbos, &c.; but these are most of them very small.

Observations on a sort of Libella, or Ephemeron. By Mr. PETER COLLINSON.-[1746.]

WALKING by the river's side at Winchester, Mr. C. was told, that now was the time of year that the May-flies, a species of libella, came up out of the waters, and were seen for a few days, and then disappeared.

May 26. 1744, he was first shown it by the name of Mayfly, on account of its annual appearance in that month. It lies all the year, except a few days, in the bottom or sides of the river; and nearly resembles the nymph of the small common libellas; but when it is mature, it rises up to the surface of the water, and splits open its case; then, with great agility, up springs the new animal, with a slender body, with four blackish-veined transparent shining wings, having four black spots in the upper wings, the under wings being much smaller than the upper ones: it has three long hairs in its tail.

The next business, after this animal is disengaged from the water, is flying about to find a proper place to fix on, as trees, bushes, &c. to wait for its approaching change, which is effected in two or three days. The first hint he received of this wonderful operation, was seeing their exuviæ hanging on a hedge. He then collected a great many, and put them in boxes; and by strictly observing them, he could tell when they were ready to put off their old clothes, though but so lately put on.

He had the pleasure to show his friends one that he held on his finger all the while it performed this great work: it was surprising to see how easily the back part of the fly split open, and produced the new birth, which he could not perceive to partake of any thing from its parent; but leaves head, body, wings, legs, and even its three-haired tail behind, or the cases of them. After it has reposed itself awhile, it flies with great briskness to seek its mate.

By much the greater numbers perish on the waters, which are covered with them. This is the end of the females; but the males never resort to the river that he could perceive: after they have done their office, they drop down, languish, and die, under the trees and bushes,

He observed that this species of libella abounded most with females; which was very necessary, considering the many enemies they have during their short appearance; for both birds and fish are very fond of them, and doubtless under the water they are a food for small aquatic animals.

What is further remarkable in this surprising creature is, that in a life of three or four days it eats nothing, seems to have no apparatus for that purpose, but brings up with it out of the water sufficient support to enable it to shed its skin, and perform the principal ends of life with great vivacity.

On the Perpendicular Ascent of Eels. By Mr. WM. ARDERON, F. R. S.-[1747.]

ON reading, some years before, what Dr. Plot, in his History of Staffordshire, relates concerning the passage of eels across meadows, in the night-time, from pond to pond, Mr. A. could hardly forbear thinking that the gentleman must have been deceived; but what Mr. A. has lately seen gives him great reason to believe that account to be strictly true.

On June 12. 1745, while viewing the flood-gates belonging to the water-works in the city of Norwich, he beheld a great number of eels sliding up them and the posts adjacent, notwithstanding they all stood perpendicular to the horizon, and five or six feet above the surface of the pool below the waterworks. They ascended these posts and gates, till they came into the dam above. And, what makes the matter appear still more strange, they slid up with the utmost facility and readiness; though many of the boards and posts were quite dry, and as smooth as a common plane had left them.

He observed, that at first they thrust their heads, and about half their bodies, out of the water, and held them up against the wood-work for some time: probably till they found the glutinous matter, which is constantly about their bodies, become sufficiently thick or viscid, by being exposed to the air, to sustain their weight: then they would begin tɔ ascend directly upwards, with as much seeming ease, as if they had been sliding along the level ground; and thus they continued to do, till they got into the dam above.

On Birds of Passage. By Mr. MARK CATESBY, F.R.S.

THE places to which birds of passage retreat when they leave us, are first of all to be enquired after, and then it will be proper to examine by what route, and in what manner,

they convey themselves to such places. The reports of their lying torpid in caverns and hollow trees, and of their resting in the same state at the bottom of deep waters, are so ill attested, and absurd in themselves, that the bare mention of them is more than they deserve.

The various conjectures concerning the places to which birds of passage retire, are occasioned by the want of ocular testimony to bring the matter to some certainty. But if the immenseness of the globe be considered, and the vast tracts of land which still remain unknown to us, it is no wonder that we are yet unacquainted with the retreat of these itinerant birds. On this head Mr. C. agrees in the general opinion of their passing to other countries by the common natural way of flying, with this additional conjecture, that the places to which they retire, lie probably in the same latitude in the southern hemisphere, as the places from whence they depart; where the seasons reverting, they may enjoy the like temperature of air.

It may be objected, that places of the same latitude in the southern hemisphere may be divided by too wide a tract of sea for them to pass over. But why then may not some other parts of the southern hemisphere serve their turn? This seems more reasonable, than that they should remain on our side of the northern tropic; within a few degrees of which, at the winter solstice, it is so cold, as frequently to produce snow; which, by dispersing such insects as birds that feed on the wing, and particularly the swallow kinds, subsist on, must make them perish inevitably, were they not to change their quarters for those more favourable climes, where a continuance of warm weather affords their natural and proper food. This their sagacity dictates to them, and is the apparent cause of their periodically leaving us at the approach of winter, before flies are so dissipated by cold and winds as to be found no longer in the air, though they may with other insects be met with in holes and hidden recesses, and serve to subsist other birds of passage.

What Mr. C. infers from hence is, that as swallows cannot continue and subsist so long in cold seasons as other birds of passage, they are necessitated to visit us somewhat later, and to depart sooner; for though nightingales, and other birds of passage, are not often seen or observed after they cease singing, yet he has frequently noticed them in their solitary coverts a month after the departure of swallows. From these reasons he concludes, that birds of passage, particularly swallows, are necessitated to pass the tropic of Cancer; but