gestion of the flesh had time to be more completely per formed, and I made no doubt of finding it so. Upon cutting the thread and removing the gratings, I looked through the tube, as through a prospect glass, and perceived it to be above half empty throughout the whole length; so that it seemed plain that there could not be so much matter in the cavity, as I had introduced. The greatest part I found to be a whitish grey pap of a much slenderer consistence than the paste of the former experiment. It was indeed liquid, and so far, it is probable, part of it might have escaped through the meshes of the grating.

There was, however, a small portion of the beef remaining under its first form, but of a much paler hue, and not of so firm a consistence. It was parted into three so minute morsels, that being washed and gently drained, and then weighed, they were but six grains, or an eighth of the original. They were so very tender as to manifest an approaching dissolution; for having put them in the palm of my hand, and worked them tenderly with the top of a finger, as with a pestle, they immediately became as a paste.

In both the experiments, the pap, the paste, and the small portion of remaining flesh, had not the least ill scent of tainted meat; they only smelled a little faint, but not at all strong.

It was natural to desire to know how far the power of this dissolvent could exert itself, whose existence had been sufficiently proved; and if it were capable of acting effec tually upon bones. Those which I first made trial of were of the softest kind, namely of a chicken a month old, no bigger than a quail. I filled the tube with six pieces, four whereof were of the wings, the others of the thighs, cut to a fit length for their reception. They weighed all together but 26 grains. The tube being grated as before, I madẹ the buzzard swallow it. It remained in his stomach not more than 24 hours; after which, upon taking off the grating and looking for the bones, I could not perceive the least remain of them. It seemed that they had undergone a quicker and easier digestion than the flesh; for there was nothing left in the tube but a little gelatinous substance, most of which adhered to the inside of one of the gratings.

In another trial I made use of one of the hardest of bones, the rib of an ox; two pieces of which I inclosed in the tube. There was none of the cavernous cellular part about them, but all as compact as ivory, weighing 40 grains. These resisted the dissolvent more than the tender ones had done; for after 24 hours they had lost but 18 grains, or

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 being 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 never omit 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 kept 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 conditioned to oppose 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 flesh, and the other half with corn. None of these experiments discovered the least alteration in any one grain of corn by the dissolvent. All 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 room 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 à little macerated from the warmth it was confined in. It tasted somewhat eager 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

VOL. II.

Ff

can do no more with vegetables, than that menstruum can do with silver? We can scarcely hope to procure of this dissolving liquor, wherewithal to furnish variety of trials sufficient 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 was 50 grains of the liquor, which I could easily squeeze into a vessel proper for keeping it. This experiment suffices to shew that we may become masters of a considerable quantity of it. buzzard may 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.

DE REAUMUR.

A

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, hath 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 the 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 shook off thirty at least.

To the naked eye they appear smaller 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 that 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 ap pear 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 flies, 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 such 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 particular 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 sometime 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 electrised 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 no, I will not undertake to determine.

1753, Νου.