the lower end of these pipes were first lifted up. These air barrels were fitted with tackle proper to make them rise and fall alternately, like to buckets in a well. In their descent they were directed by lines fastened at the under edge of the bell to the man standing on the stage to receive them, who, by taking up the ends of the pipes above the surface of the water in the bell, gave occasion for the water in the barrels to force all the air in the upper parts into the bell, while it entered below, and filled the barrels ; and as soon as one was discharged, by a signal given, it was drawn up, and the other descended to be ready for use. As the cold air rushed into the bell from below, it expelled the hot air through a cock at the top of the bell, which was then opened for that purpose. By this method, air is communicated so quick, and in such plenty, that the doctor tells us, he himself was one of the five who was at the bottom in nine or ten fathoms water, for above an hour and a half at a time, without any sort of ill consequence; and he might have continued there as long as he pleased, for any thing that appeared to the contrary. In going down it is necessary it should be very gentle at first, that the dense air may be inspired, to keep up, by its spring, a balance to the pressure of the air in the bell: upon each twelve feet descent, the bell is stopped, and the water that enters is driven out by letting in three or four barrels of fresh air. By the glass above, so much light was transmitted, when the sun shone, that he could see perfectly well to write and read, and by the return of the airbarrels, he could send up orders, written with an iron pen, on small pieces of lead, directing, that

they were to be moved from place to place: but in the dark weather, when the sea was rough and troubled, it would be as dark as night in the bell; but then the doctor perceived he could keep a candle burning in the bell as long as he pleased, it being found, by experiment, that one candle consumes much about the same quantity of confined air, as one man does, viz. about a gallon per minute. The only inconvenience the doctor complained of was, that upon first going down, they felt a small pain in their ears, as if the end of a quill were forThis may cibly thrust into the hole of the ear. proceed from its being some time before the air can get from the mouth, through the small canal of the eustachian tube, which leads to the inner cavity of the ear, where, when it comes, it makes an equilibrium with the outward air, pressing on the tympanum, and thus the pain, for a short time, ceases: then descending lower, the pain of the ear returns, and is again abated; and so on, till the bottom is gained, where the air is of the same den. sity continually. This bell was so improved by the doctor, that he could detach one of his divers to the distance of fifty or a hundred yards from it, by a contrivance of a cap, or head-piece, somewhat like an inverted hand-basket, with a glass in the fore-part, for him to see his way through. This cap was of lead, and made to fit quite close about his shoulders in the top of it was fixed a flexible pipe, communicating with the bell, and by which he had air, when he wanted, by turning a There was also stop-cock near his head-piece. another cock at the end in the bell, to prevent any accident happening from the person without. This