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198 PONDS ON THE SUMMITS OF CHALK HILLS.

containing pernaps not more than two or three hundred hogsheads of water, yet never is known to fail, though it affords drink for three hundred or four hundred sheep, and for at least twenty head of large cattle besides. This pond, it is true, is overhung with two moderate beeches, that, doubtless, at times, afford it much supply; but then we have others as small, that, without the aid of trees, and in spite of evaporation from sun and wind, and perpetual consumption by cattle, yet constantly maintain a moderate share of water, without overflowing in the wettest seasons, as they would do if supplied by springs. By my journal of May, 1775, it appears that "the small and even considerable ponds on the vales are now dried up, while the small ponds on the very tops of hills are but little affected." Can this difference be accounted for from evaporation alone, which certainly is more prevalent in bottoms? or rather have not those elevated pools some unnoticed recruits, which in the night-time counterbalance the waste of the day; without which, the cattle alone must soon exhaust them? And here it will be necessary to enter more minutely into the cause. Dr Hales, in his Vegetable Statics, advances, from experiment, that "the moister the earth is, the more dew falls on it in a night; and more than a double quantity of dew falls on an equal surface of moist earth." Hence we see that water, by its coolness, is enabled to assimilate to itself a large quantity of moisture nightly by condensation; and that the air, when loaded with fogs and vapours, and even with copious dews, can alone advance a considerable and neverfailing resource. * Persons that are much abroad, and travel early and late, such as shepherds, fishermen, &c. can tell what prodigious fogs prevail in the night on elevated downs, even in the hottest parts of summer; and how much the surfaces of things are drenched by those swimming vapours, though, to the senses, all the while, little moisture seems to fall.

*Fogs are much more frequent in cold seasons, and cold countries, than in such as are warm; because, in the former, the aqueous particles, being condensed almost as soon as they proceed from the surface of the earth, are incapable of rising into the higher portions of the atmosphere. If the cold be augmented, the fog freezes, attaching itself in small icicles to the branches of trees, and to the hair and clothes of persons exposed to it, to the blades of grass, and other substances.- ED.

LETTER LXXII.

TO THE HON. DAINES BARRINGTON.

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SELBORNE, April 3, 1776. DEAR SIR, Monsieur Herissant, a French anatomist, seems persuaded that he has discovered the reason why cuckoos do not hatch their own eggs; the impediment, he supposes, arises from the internal structure of their parts, which incapacitates them for incubation. According to this gentleman, the crop, or craw, of a cuckoo, does not lie before the sternum at the bottom of the neck, as in the gallinæ, columbæ, &c. but immediately behind it, on and over the bowels, so as to make a large protuberance in the belly.*

Induced by this assertion, we procured a cuckoo; and, cutting open the breast-bone, and exposing the intestines to sight, found the crop lying as mentioned above. This stomach was large and round, and stuffed hard, like a pin-cushion, with food, which, upon nice examination, we found to consist of various insects; such as small scarabs, spiders, and dragonflies; the last of which we have seen cuckoos catching on the wing, as they were just emerging out of the aurelia state. Among this farrago also were to be seen maggots, and many seeds, which belonged either to gooseberries, currants, cranberries, or some such fruit; so that these birds apparently subsist on insects and fruits; nor was there the least appearance of bones, feathers, or fur, to support the idle notion of their being birds of prey.†

The sternum in this bird seemed to us to be remarkably short, between which and the anus lay the crop, or craw, and, immediately behind that, the bowels against the back-bone.

It must be allowed, as this anatomist observes, that the crop, placed just below the bowels, must, especially when full, be in a very uneasy situation during the business of incubation; yet the test will be, to examine whether birds that are actually known to sit for certain are not formed in a similar manner.

* Histoire de l'Academie Royale, 1752.

Sir William Jardine says, that when cuckoos have fed much on some of the large hairy caterpillars so common on the northern moors, the stomach becomes coated with the short hairs, which may have given rise to the opinion that they are predatory. But has not Sir William mistaken the fibrous structure of the stomach for these hairs? Its American congeners, the yellow-billed cuckoo, and the black-billed cuckoo, ròb birds of their eggs; and the latter feeds on fresh water shell-fish. ED.

This inquiry I proposed to myself to make with a fern-cwl, or goat-sucker, as soon as opportunity offered: because, if their formation proves the same, the reason for incapacity in the cuckoo will be allowed to have been taken up somewhat hastily.

Not long after, a fern-owl was procured, which, from its habits and shape, we suspected might resemble the cuckoo in its internal construction. Nor were our suspicions ill grounded; for, upon the dissection, the crop, or craw, also lay behind the sternum, immediately on the viscera, between them and the skin of the belly. It was bulky, and stuffed hard with large phalana, moths of several sorts, and their eggs, which, no doubt, had been forced out of these insects by the action of swallowing.

Now, as it appears that this bird, which is so well known to practise incubation, is formed in a similar manner with cuckoos, Monsieur Herissant's conjecture, that cuckoos are incapable of incubation from the disposition of their intestines, seems to fall to the ground: and we are still at a loss for the cause of that strange and singular peculiarity in the instance of the cuculus canorus.

We found the case to be the same with the ring-tail hawk, in respect to formation; and, as far as I can recollect, with the swift; and probably it is so with many more sorts of birds that are not granivorous.

LETTER LXXIII.

TO THE HON. DAINES BARRINGTON.

SELBORNE, April 29, 1776. DEAR SIR, On August the 4th, 1775, we surprised a large viper, which seemed very heavy and bloated, as it lay in the grass, basking in the sun. When we came to cut it up, we found that the abdomen was crowded with young, fifteen in number; the shortest of which measured full seven inches, and were about the size of full-grown earth-worms. This little fry issued into the world with the true viper spirit about them, shewing great alertness as soon as disengaged from the belly of the dam: they twisted and wriggled about, and set themselves up, and gaped very wide, when touched with a stick, shewing manifest tokens of menace and defiance, though as yet they had no manner of fangs that we could find, even with the help of our glasses..

To a thinking mind, nothing is more wonderful than that early instinct which impresses young animals with the notion of the situation of their natural weapons, and of using them properly in their own defence, even before those weapons subsist or are formed. * Thus a young cock will spar at his adversary before his spurs are grown; and a calf or lamb will push with their heads before their horns are sprouted. In the same manner did these young adders attempt to bite before their fangs were in being. The dam, however, was furnished with very formidable ones, which we lifted up, (for they fold down when not used,) and cut them off with the point of our scissars.

There was little room to suppose that this brood had ever been in the open air before, and that they were taken in for refuge, at the mouth of the dam, when she perceived that danger was approaching; because then, probably, we should have found them somewhere in the neck, and not in the abdomen.

LETTER LXXIV.

TO THE HON. DAINES BARRINGTON.

CASTRATION has a strange effect: it emasculates both man, beast, and bird, and brings them to a near resemblance of the other sex. Thus, eunuchs have smooth unmuscular arms, thighs, and legs; and broad hips, and beardless chins, and squeaking voices. Gelt stags and bucks have hornless heads, like hinds and does. Thus wethers have small horns, like ewes; and oxen large bent horns, and hoarse voices when they low, like cows: for bulls have short straight horns; and though they mutter and grumble in a deep tremendous tone, yet they low in a shrill high key. Capons have small combs and gills, and look pallid about the head like pullets; they also walk without any parade, and hover chickens like hens. Barrow-hogs have also small tusks like sows.†

* An adder with two distinct heads, which lived three days, taken with five others from the body of an old one, found in a ditch at Drumlanrig, Dumfriesshire, is now in the museum of Mr Thomas Grierson, Baitford, near Thornhill. - ED.

† After castration animals generally lose their spirit, although, in the instance of horses, this is by no means always the case. The following fact is a strong evidence of this: - The horse of a nobleman in Ireland ran at a man, seized him with his teeth by the arm, which he broke; he then threw him down, and lay upon him. Every effort to get him off.

Thus far it is plain, that the deprivation of masculine vigour puts a stop to the growth of those parts or appendages that are looked upon as its insignia. But the ingenious Mr Lisle, in his book on husbandry, carries it much farther; for he says, that the loss of those insignia alone has sometimes a strange effect on the ability itself. He had a boar so fierce and venereous that, to prevent mischief, orders were given for his tusks to be broken off. No sooner had the beast suffered this injury than his powers forsook him, and he neglected those females to whom before he was passionately attached, and from whom no fences could restrain him.

LETTER LXXV.

TO THE HON. DAINES BARRINGTON.

THE natural term of a hog's life is little known, and the reason is plain, because it is neither profitable nor convenient to keep that turbulent animal to the full extent of its time; however, my neighbour, a man of substance, who had no occasion to study every little advantage to a nicety, kept a half-bred Bantam sow, who was as thick as she was long, and whose belly swept on the ground, till she was advanced to her seventeenth year; at which period, she shewed some tokens of age by the decay of her teeth, and the decline of her fertility.

For about ten years, this prolific mother produced two litters in the year, of about ten at a time, and once above twenty at a litter; but, as there were near double the number of pigs to that of teats, many died. From long experience in the world, this female was grown very sagacious and artful. When she found occasion to converse with a boar, she used to open all the intervening gates, and march, by herself, up to a distant farm where one was kept, and when her purpose was served, would return by the same means. At the age of about fifteen, her litters began to be reduced to four or five; and such a litter she exhibited when in her fatting-pen. She proved, when fat, good bacon, juicy, and tender; the rind, or sward, was remarkably thin. At a moderate computation, she was allowed to have been the fruitful parent of three

proved unavailing, and they were forced to shoot nim. The only reason could be assigned for such ferocity was, that he had been castrated by this man some time before, which the animal seems to have remembered. -ED.

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