Having procured a duckling, that was yet callow, we conveyed her into the same receiver wherein the former had been included, and observed, that, though for a while she appeared not much disquieted, whilst the air was pumping out of the glass, yet before the first minute was quite ended, she gave manifest tokens of being much disordered; and the operation being continued a while longer, she grew so much worse, that several convulsive motions which she fell into before a second minute was expired, obliged us to let in the air upon her, whereby she quickly recovered.

Considering that vipers are animals endowed with lungs, (though of a different structure from those of men, dogs, cats, birds, &c.) and that their blood is actually cold, I thought it might, upon both those accounts, be very well worth trying what effect the withdrawing and absence of the air would have upon animals so constituted.

We included a viper in a small receiver, and as we drew out the air, she began to swell, and afforded us these phenomena:- 1. It was a good while after we had left pumping, ere the viper began to swell so much as to be forced to gape, which afterwards she did.-2. That she continued, by our estimate, above 2 hours in the exhausted receiver without giving clear proof of her being killed. - 3. That after she was once so swelled, as to be compelled to open her jaws, she appeared slender and lank again, and yet very soon after appeared swelled again, and had her jaws disjoined as before.

We took a viper, and including her in the largest sort of small receivers, we emptied the glass very carefully, and the viper moved up and down within, as if to seek for air, and after a while foamed a little at the mouth, and left some of the foam sticking to the inside of the glass: her body swelled not considerably, and her neck less, till a considerable time after we had left pumping; but afterwards the body and neck grew prodigiously tumid, and a blister appeared upon. the back. An hour and a half after the exhaustion of the receiver, the distended viper gave manifest signs of life; but we observed none afterwards.

To these experiments upon vipers, I shall add one made upon an ordinary harmless snake. We included such an animal, together with a gauge, in a pretty portable receiver, which being exhausted and well secured against the ingress of the air, was laid aside in a quiet place, where it continued from 10 or 11 o'clock in the forenoon till about nine the next morning; and then my occasions calling me abroad, I looked upon the snake; which though he seemed to be dead,

and gave no signs of life upon the shaking of the receiver, yet upon holding the glass a convenient distance from a moderate fire, he did in a short time manifest himself to be alive by several tokens, and even by putting forth his forked tongue. In that condition I left him, and by reason of several avocations, came not to look upon him again till early in the afternoon of the next day, at which time he was grown past recovery, and his jaws, which were formerly shut, gaped exceedingly wide, as if they had been stretched open by some external violence.

The same considerations that induced me to make trials upon vipers, invited me also to make several upon frogs.

We took a large lusty frog, and having included her in a small receiver, we drew out the air, and left her not very much swelled, and able to move her throat from time to time, though not so fast as when she freely breathed before the exsuction of the air. She continued alive about two hours, that we took notice of, sometimes removing from the one side of the receiver to the other; but she swelled more than before, and did not appear by any motion of her throat or thorax to exercise respiration, but her head was not very much swelled, nor her mouth forced open. After she had remained there somewhat above three hours, perceiving no sign of life in her, we let in the air upon her, at which the tumid body shrunk very much, but seemed not to have any other change wrought in it; and though we took her out of the receiver, yet in the free air itself she continued to appearance dead. Nevertheless to see the utmost of the experiment, having caused her to be laid upon the grass in a garden all night, the next morning we found her perfectly alive again.

We took a small frog, and having conveyed her into a very small portable receiver, began to pump out the air. At first she was lively enough, but when the air was considerably withdrawn, she appeared to be very much disquieted, leaping sometimes after an odd manner, as it were to get out of the uneasy prison, but yet not so, but that after the operation was ended, and the receiver taken off, the frog was perfectly alive, and continued to appear so near an hour, though the abdomen was very much, and the throat somewhat, extended; this latter part having also left that wonted panting motion, that is supposed to argue and accompany the respiration of frogs. At the end of about 3 hours, after the removal of the receiver from the pump, the air was let in; whereupon the abdomen, which by that time was strangely swelled, did

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not only subside, but seemed to have a great cavity in it, as the throat also proportionably had; which cavities continued, the frog being gone past all recovery.

It might assist us in making the more rational conjectures about the phenomena of divers of our experiments, if we knew what quantity of aërial substance is usually found in the liquors we employ about them, especially in that most common of them, water. And, therefore, though it be very difficult (if at all possible) to determine the proportion of the air that lurks in water with any kind of certainty, many circumstances making it subject to vary very much, yet to make the best estimate I easily could, where none at all that I know of has been hitherto made by any man, I considered that it might afford us some light, if we discovered at least what proportion as to bulk the air latent in a quantity of water would have to the liquor it came from, when the aërial particles should be gathered together into one place.

On pumping out the air, numerous bubbles disclosed themselves, ascending nimbly to the upper part of the glass, where they made a kind of froth or foam. This done, the pump was suffered to rest a while, to give the aërial particles lodged in the water time to separate themselves and emerge, which when they had done the pump was plied again, for fear some air should have stolen into so large a receiver. These vicissitudes of pumping and resting lasted for a considerable time, till at length the bubbles began to be very rare, and we weary of waiting any longer; soon after which the external air was let into the receiver, and it appeared somewhat strange to the spectators, that notwithstanding so great a multitude of bubbles as had escaped out of the water, I could not, by attentively comparing the place where the surface of the water rested at first with that where it now stood, discern the difference to amount to above a hair's breadth, if so much, and the chief operator in the experiment professed that, for his part, he could not perceive any difference at all.

Having had frequent occasions to observe how quickly those animals, whose blood is actually warm, did expire in our vacuum, and that even those animals with lungs, whose blood was actually cold, were not able to live any considerable time there, I thought it worth while, though extremely difficult to try, whether there might not be some ways yet unpractised, either to make such animals as nature endows with lungs live without respiration, or at least to bring such insects, and other animals, as can already live without air, to move also without it in our vacuum.

We took a number of tadpoles, and put them with a convenient quantity of water into a portable receiver of a round form, and observed, that at the first exsuction of the air they rose to the top of the water, though most of them subsided again, till the next exsuction raised them. The receiver being exhausted, they continued restless, moving all of them in the top of the water, and though some of them seemed to endeavour to go to the bottom, and dived some part of the way, especially with their heads, yet they were immediately buoyed up again. Within an hour or a little more they were all motionless, and lay floating on the water; wherefore I opened the receiver, upon which the air rushed in, and almost all of them presently sunk to the bottom, but none of them recovered.

We took five or six caterpillars of the same sort; but 1 could not tell to what ultimate species the writers about insects referred them. These being put into a separate receiver of a moderate size, had the air drawn away from them, and carefully kept from returning. But notwithstanding this deprivation of air, I found them, about an hour after, moving to and fro in the receiver; and even above two hours after that, I could, by shaking the vessel, excite in them some motions, that I did not suspect to be convulsive. But looking upon them again some time before I was to go to bed, about 10 hours after they were first included, they seemed to be quite dead, and though the air was forthwith restored to them, they continued to appear so, till I went to bed; yet I thought fit to try, whether time might not at length recover them, and leaving them all night in the receiver, I found the next day, that three if not four of them were perfectly recovered.

We closed up divers ordinary flies, and a bee or wasp; all which, when the air was fully withdrawn, lay as dead, save that for a very few minutes some of them had convulsive motions in their legs. They continued in this state 48 hours, after which the air was let in upon them, and that not producing any signs of life in them, they were laid in the meridian sun, but not any of them seemed in any degree to

recover.

We conveyed then a number of mites, together with the mouldy cheese they were bred in to nourish them, into three or four portable receivers (which were all of them very small) not much differing in size. As soon as ever one of the reccivers was removed from the engine, I looked with great attention upon it; and though just before the withdrawing

of the air the mites were seen to move up and down in it, yet within a few minutes after the receiver was applied to the engine, I could discern in them no life at all, nor was any perceived by some younger eyes than mine, whereunto I exposed them. Nay, by the help of a double convex glass (that was so set in a frame as to serve me as a microscope on such occasions) I was not able to see any of them stir up and down.

The Manner of Spiders projecting their Threads. cated by Mr. JOHN RAY.—[1670.]

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I HAVE seen spiders shoot their webs three yards long before they begin to sail; and then they will, as it were, fly away incredibly swift: which phenomenon somewhat puzzles me, as the air seldom moves a quarter so fast as they seem to fly. In general they project their threads single, without dividing or forking at all to be seen in them: sometimes they shoot the thread upward, and will mount up with it in a line almost perpendicular; and at other times, they project it parallel to the horizon; as you may often see by their threads that run from one tree to another, and likewise in chambers from one wall to another. I confess this observation at first made me think that they could fly, because I could not conceive how a thread could be drawn so parallel to the horizon between two walls or trees, as above mentioned, unless the spider flew through the air in a straight line.

They often fasten their threads in several places to the things they creep over: the manner is, by beating their tails against them as they creep along. By this frequent beating in of their thread among the asperities of the place where they creep, they either secure it against the wind, that it be not easily blown away, or else, while they hang by it, if one stick breaks another holds fast; so that they do not fall to the ground.

An Account by Dr. ERASMUS BARTHOLIN, on a Crystal-like Body, sent to him from Iceland. [1671.]

THE inhabitants of Iceland and our own merchants inform us, that this kind of crystal is found in divers places of that country; but chiefly dug out of a very high mountain, not far from the bay of Roerfiord, which lies in 65 degrees latitude. That the mountain has its whole outside made up of this substance, without a necessity of digging deep for it. That