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about half their weight. Each bone had a small drop of gelatinous matter at either end, being doubtless part of the substance which had been dissolved. That which remained under the form of bone, was hard; and these two fragments were not entirely dissolved, that is, they were not reduced to less than four grains, after having been twice more introduced into the bird's stomach.
The true carnivorous birds, such as our buzzard, feed only on the flesh of other birds, and that of quadrupeds and reptiles: no degree of hunger will induce them to swallow grain of any kind. Is this because the dissolvent of their stomachs can act only upon flesh and bones, and not upon vegetable productions? Nature has taught animals infallible lessons, such as they most stand in need of, and which they neveromit to pursue. It was reasonable therefore to presume, and curious to be satisfied, that this dissolvent in the buzzard's stomach, of such efficacy upon flesh and bones, would fail upon substances of the vegetable kingdom. I have already related an experiment, several times repeated, which seems to prove it. The thread gratings of our tubes always remained entire, without damage to any single twist.
The tubes, however, indicated very easy means of proving the power of the dissolvent on vegetable substances, which seemed less capable of opposing it, than strong and dry fibres of plants. I gave several tubes, filled with corns of wheat and barley, to the buzzard, both in the husk and without it, and also boiled. In others I put a bit of the crumb of bread, as long as the tube, and stuck with different grains; and lastly, one half of another tube was filled with Hesh, and the other half with corn. None of these experiments discovered the least alteration in any one grain of corn by the dissolvent. À!l came out as they were put in, saving a little swelling, such as would have been from a like continuance in any damp place. The.crumb of bread seemed to have been a little operated upon, as though it had been chewed, but it was not converted to a paste, as the flesh was, that was included along with the grain.
I have reason to think that the dissolvent can operate but little more on fruit than on grain. A piece of ripe orange pear weighing 29 grains, after remaining 24 hours in the buzzard's stomach, came out unaltered; appearing only a little macerated from the warmth it was confined in. It tasted somewhat aigre and had lost only four grains of its weight.
Now what must be the nature of this liquor, which has the like power on flesh and bones as aqua regia on gold; and
can do no more with vegetables, than that menstruưm can do with silver? We can scarcely hope to procure enough of this dissolving liquor to furnish a sufficient variety of trials to discover its several properties; but our tubes which have stood us so much in stead in examining into the affair of digestion, so far can supply us as to furnish proof enough of its nature. If a tube were filled with a sponge, a substance which no bird of prey feeds upon, and which, from what has appeared above, his stomach cannot digest; it should seem probable that it would imbibe the dissolvent. In short, I introduced several bits into a tube, taking care not to press them too close together, and grated up the ends... These the buzzard swallowed, and rejected as usual. The sponge, before it was put in, weighed only 13 grains; but taken out of the tube it weighed 63. Here then were 50 grains of the liquor, which I could easily squeeze into a vessel keeping it. This experiment suffices to shew that we may become masters of a considerable quantity of it. A buzzard
be made to swallow two or three tubes filled with
sponge in a day. But if, instead of a buzzard, the thing were to be done by a vulture or eagle, it might not be difficult to obtain a good glass-full of the dissolvent. 1753, July, Aug. and Sept.
XIV. The Cause of the Lustre or Resplendency of the Sea-water
in the Night time, discovered and explained. THE splendour of the sea water during the night, has long been a subject of admiration, and upon the coasts in the neighbourhood of the town of Chioggia, it is particularly remarkable; at first sight one would imagine that the brilliant images of the fixed stars were reflected by the sea, and when the sea is agitated by winds, or pierced by the strokes of oars, this brightness becomes much more vivid and copious, especially in places abounding with the alga marina, or sea weed. This beautiful phenomenon, which continues in our parts, from the beginning of summer till autumn, hath often engaged my attention, and at length excited an earnest desire to discover, if possible, the true cause of it.
One fine summer night I walked out upon the sea-shore, and after having observed this shining water for some time, i took a vessel full of it home with me. I placed it in a dark room, and observed, that as often as I disturbed and agitated she water with my hand, a very bright light issued from it.
I then passed the water through a very close-woven linen cloth, to try if it would still retain its splendour after such a percolation. But, notwithstanding I shook and agitated it in the most violent manner, I could not excite the least luminousness in it. The linen cloth, however, afforded the most charming spectacle imaginable. It was covered with an infinity of lucid particles; a proof that the water owed its splendour to certain heterogeneous shining corpuscles, copiously disseminated through it. These corpuscles are also very numerous upon
the leaves of the alga ; from some leaves I have shaken off thirty at least.
To the naked eye they appearsmaller than the finest hairs; their colour is of a deep yellow, and their substance delicate beyond imagination. But having a mind to examine them more curiously, I furnished myself with a good microscope, and was soon convinced that these luminous atoms are really living animals of a very singular structure; and, from the brightness of their lustre, I thought' myself authorised to name them marine glow-worms.
These little animals, similar in some respect to caterpillars, and other insects of that species, are composed of eleven articulations, or annuli, a number which, according to the celebrated Malpighi, is peculiar to the whole vermicular race. Upon these annuli, and near the belly of the animal, are a sort of small fins or wings, which seem to be the instruments of its motion. It has two small horns issuing from the fore part of its head, and its tail is cleft in two.
I have already observed, that these worms are most numerous where the alga abounds. Upon this weed they appear about the beginning of summer, and soon after multiply prodigiously, and spread themselves over the whole surface of the waters. It is probably the heat of the season that causes these animals to lay their eggs, it having the same influence upon other aquatic insects, according to the discoveries of the learned Mr. Derham. We learn also from M. de Reaumur's observations, that terrestrial insects of this species, shine only in the heighth of summer, and that their shining is caused by a particular effervescence excited in them during the time of their copulation,
We read of shining Aies, which in several parts of the world, give light to travellers in the hottest nights of summer. We are told too that in some parts of the Indies, there are great numbers of shining worms, which, in very hot nights, emit luminous particles so copiously that the bushes and thickets seem to be on fire. But in one respect our marine glow-worms excel all their lucid brethren of the
terrestrial species, for these latter emit light only at a pare ticular spot near the tail, whereas the whole body of the former is luminous. There is also one further particular to be observed, with respect to these marine animals, which is, that they do not emit the least light so long as they are still and motionless, but the parts of their little bodies are no sooner moved and agitated, than they begin to sparkle with a very extraordinary lustre. From hence may we not conclude, that their shining depends upon their motion, and is probably excited by a strong vibration of the constituent parts of their bodies, since the luminous effusions, or corruscations, seem to be exactly proportionable to the briskness and vigour of their motions.
It is to be remarked too, that when one of these little animals is cut to pieces, every piece emits a vivid light for some time, probably so long as the convulsive motion of the dying parts continues; for we know that the parts of certain fishes and insects will continue to move some time after they have been separated from the rest of the body.
After this, we need not wonder that mariners and fishermen foretel a storm, or change of weather, when they see the sea and lakes shine in an unusual manner; for at such times it may be expected that these little animals are agitated and disturbed more than common. The same thing is observable in flies and other winged insects, which are strongly affected upon an approaching alteration of the weather, and fly about in great disorder.
Many philosophers of the first rank, have imagined that the luminousness of the sea-water, in the night season, is, occasioned by some electric matter. The surface of the sea, say they, having been exposed all the summer to the impulse and action of the solar rays, when it begins to be agitated by the autumnal winds, throws out luminous sparks. perfectly similar to those which issue from electrical bodies.' But ocular demonstration now convinces us that this brightness is to be ascribed to these little animals. The shining of these animals may indeed proceed from electric matter contained in them, and agitated by vibration or some other internal motion, but whether it be so or not, I will not undertake to determine.
XV. Electricity in Cats. MR. URBAN, The phenomena of electricity, which has so many surprising properties, seem to be of two sorts, natural and artificial ; the last is to be obtained from all bodies naturally susceptible of it, as glass, &c. in which the property lies dormant till excited to act by friction, or some other violent motion.
Natural electricity is common almost to all animals, especially those destined to catch their prey by night: cats have this property in the greatest degree of any animal we are acquainted with; their fur or hair is surprisingly electrical. If it be gently raised up it avoids the touch till it be forced to it, and by stroking their backs in the dark, the emanations of electrical fire are extremely quick and vibrative from it, followed by a crackling noise as from glass tubes when their electrical atmosphere is struck. It appears to me of singular use to animals destined to catch their prey in the dark; they give a sudden and quick erection to their fur, which raises the electrical fire, and this, by its quickness rushing along the long pointed hairs over their eyes, and illuminating the pupilla, enables them to perceive and seize their prey. It would be worth while to inquire whether all the wild sort that catch their prey
are not endowed with the same vibrations of electrical fire. The cat is the only domestic animal of that species; but such a discovery in the ferocious kind, would still be an additional demonstration of that infinite wisdom, so easily discoverable in the most minute operations of all the works of God, and so perfectly adapted to a proper end.
I am yours, &c. 1754, March,
XVI. Heads for a Natural History of Great Britain. The following Queries are proposed to Gentlemen in the several
parts of Great Britain, where they reside, with a view of obtaining, from their Answers, a more perfect account of the Antiquities and Natural History of our Country, than has yet ap
peared. 1. W
HAT is the ancient and modern name of the parish, and its etymology?