VOL. XXVI.] PHILOSOPHICAL TRANSACTIONS. 499 



N° 297. For by that comparison it appeared, that less rain fell at Upminster, 

 than at either of the other three places. But according to these later 8 years 

 in the table, a small matter more falls at Upminster than at Paris. For the 

 mean proportion for Paris, according to former years, was above 22 inches 

 English. The proportions therefore which I shall now lay down for the yearly 

 rain of all places, whose rain I have had information of, are these; for Zurich 

 (till further observations are made) 324- inches ; for Pisa (till further observa- 

 tions also) 434- inches ; for Paris, 19 inches ; for Lisle, 24 inches ; for Towne- 

 ley in Lancashire, 42-i- inches; for Upminster 19^ inches. 



An Experiment y showing that actual Sound cannot be transmitted through a 

 Facuum. By Mr. Fr. Hauksbee, F.R.S. N° 321, p. 367. 



That the experiments already made, endeavouring to produce sound from a 

 bell in vacuo, have been altogether ineffectual, is well known. Yet that the 

 loss of it should be wholly attributed to the absence of the air, I think could 

 not without another experiment be absolutely concluded, since the following 

 query might fairly be started on this occasion ; viz. whether the sonorous body 

 in such a medium might not so suffer, or undergo such a change in its parts, 

 as to be rendered incapable of being put into such a motion as is requisite for 

 the action or production of sound. Now to bring this to the test, I contrived 

 the following experiment. 



I took a strong receiver, armed with a brass-hoop at bottom, in which I in- 

 cluded a bell as large as it could well contain. This receiver being screwed 

 strongly down to a brass-plate, with a wet leather between, was full of common 

 air, which could in no way escape. Thus secured, it was set on the pump, 

 where it was covered with another large receiver. In this manner, the air con- 

 tained between the outer and inner receivers was exhausted. Now here I 

 was sure, when the clapper should be made to strike the bell, there would be 

 actual sound produced in the inner receiver, the air in which was of the same 

 density with common air ; and could suffer no alteration by the vacuum on its 

 outside, being so strongly secured on all sides. Thus all being ready for trial, 

 the clapper was made to strike the bell ; but there was no transmission of it 

 through the vacuum, though it was certain there was actual sound produced in 

 the receiver. This plainly shows, and seems positively to confirm, that air is 

 the only medium for the propagation of sound. 



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