"I have got a most exquisitely fine Balance, and a very neat Glass Box, and have all this day been employ'd in twisting the Necks of s—in vain! ...I beg ...you will procure me one of their necks to be twisted into a little Hook according to the... the reverse of this Paper: It must be truly hermetically seal'd, air-tight ...I intend to foretell every Shower... and make great medical discovery as far as relates to the Specific Gravity of Air: and from the Quantity of Vapor.—Thus the Specific Gravity of Air, should be as the Absolute Gravity (shew'd by the Barometer) and as the Heat (shew'd by Boulton's thermometer). Now if it is not always found as these two (that is as one and inversely as the other) then the deviations at different Times must be as the Quantity of dissolved Vapour in the Air. The common s only shew when the Air is in a Disposition to receive or part with moisture, not at all the Quantity it contains."