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54
succefsive and slow, it only difsolves that pure part of the alkaline salt, which is most soluble and lefs earthy and cannot be done otherwise: hence by repeating it, the whole salt may be converted into earth, and a volatile substance, that does not appear to the senses. This and like considerations "led him to discover that the air contained in a three-pint-bottle, might hold water enough to moisten an ounce of Salt of tartar,and increase its weight; and upon repeating the experiment, I found that the water (here mixed with the air) being, perhaps, 850 times heavier than common air, must make up the largest part of the weight of this portion of air; for, if the 850th part of common air be water, the whole weight of the air must be owing to the water alone; whilst the other parts add little or nothing to the weight, or perhaps do not gravitate at all. M. [[underlined]]Deventer[[/underlined]] the famous writer upon midwifery, afsured me he had made the same observation." Shaw's Translation of Boerhaave's Chemistry Vol.I.p.400.Art.44,&45.

p. 401. This experiment did not add any thing elastic to the oil of tartar [[underlined]]per deliquium[[/underlined]] and the air's elasticity remained as perfect and strong as at first. Also p. 403 & 404, "There is no air without water, even on the tops of the highest mountains."

Inclose a Barometer in a pliant bladder, with no more air than will remain after squeezing it well together with the hand; apply a strong fire to it (taking care to keep it moist, lest it should shrink) and no manner of alteration [[strikethrough]][[/strikethrough]] in the rising or falling of the Barometer will ensue, because the action or prefsure of the air [[strikethrough]][[/strikethrough]] upon the bladder without, [[strikethrough]]is[[/strikethrough]] was a counterbalance to that within, at first, (for they were both of the same state and each contained an equal quantity of fire) now the fire rarifies the air within, makes a lefs quantity of air in a given space, but more active, and so what is lost in density is exactly made up by the action or force of the fire, for the action or prefsure without resists the swelling of the bladder, (in this experiment) and a continual equilibrum is preserved between them, if at any time they should not be in equilibro, then by the laws of hydrostatics, the nature of all fluids, and the supposition of the bladder being perfectly pliant, it would either shrink lefs or swell more until they were in equilibro. If the bladder were full blown, the case would remain the same, & be just as if the bladder was glafs, or other unpliant substance.
If the flaccid bladder be put under a receiver, upon exhausting the air, it will swell prodigiously and the mercury in the inclosed barometer will sink until the bladder is done swelling; the reason is because the outward prefsure is removed and the air within the bladder takes up a greater space than before, and consequently is more rare & occasions the barometer to fall: if only one half of the receiver be exhausted and then a strong fire applied, the same effect will ensue, as if the receiver had been more exhausted proportionally to the heat applied. W.J.