Page:Philosophical Transactions - Volume 024.djvu/432

two Atmospheres being Impell'd, and the Bell made to Ring, a notable Improvement of the Sound was then manifest. But upon the Intrusion of the 3d, 4th and 5th Atmospheres, the Bell being made to strike, the Sound seem'd not to be Propagated proportionably to the first and second which might happen by means of some Escapes of Air, or, which is much to the same purpose, the Valve, which should have hindred the Return of the Injected Air, did not hold so tight as I expected, or as it ought; but that some of the Intruded Air would repass into the Syphon, by which means the Quantities suppos'd Injected were deficient. Another reason the latter Atmospheres did not propagate the Sound as the two first, is this, altho 25 Compressions of the Syphon are equal to the Natural Content of the Recipient, yet when the Air becomes pretty strongly Condens'd, as by the Intrusion of 4 or 5 Atmospheres, the remaining Air at every stroke which will lye between the Bottom of the Embolus and the Valve (altho but little) is at the same Density at the same time as the Air in the Recipient; which, upon drawing up the forces, will extend it self to supply such a space of the Cylinder as so much common Air; and is so much short of what should be injected at every stroke, 25 of which become equal to the Natural Content of the Receiver. Hence the Deficiencies of the Real Atmospheres or Quantities, by a certain number of Strokes may be very considerable, and to account for them most difficult; and so I must leave them for the present, begging pardon for this digression. I conclude, Notwithstanding the Deficiencies are not known, yet at the end of the 5 (tho Imperfect) Atmospheres, the Bell being shaken as at first, it was the Opinion of a Gentleman then 50 yards distant, that the Sound seem'd to be almost as and as sensible as when it came to be made and expos'd in the open Air.

June the 9th, about 5 in the morning I repeated this Experiment in an open Field, known by the name ofthe