VOL. XXIV.j PHILOSOPHICAL TRANSACTIONS. 203 



second ; which might happen by means of some escapes of air, or the valve, 

 which should have hindered the return of the injected air, not holding so tight 

 as it ought; but that some of the intruded air would repass into the syphon, 

 by which means the quantities supposed injected were deficient. Another 

 reason why the latter atmospheres did not propagate the sound as the two 

 first, is this ; though 25 compressions of the syphon are equal to the natural 

 content of the recipient, yet when the air becomes pretty strongly condensed, 

 as by the intrusion of 4 or 5 atmospheres, the remaining air at every stroke, 

 which will lie between the bottom of the embolus and the valve (though but 

 little) is at the same density at the same time as the air in the recipient ; which, 

 on drawing up the forcer, will extend itself, to supply such a space of the cy- 

 linder 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, very 

 difficult. Notwithstanding the deficiencies are not known, yet at the end of 

 the 5 (though imperfect) atmospheres, the bell being shaken as at first, it 

 was the opinion of a gentleman then 50 yards distant, that the sound seemed 

 to be almost as sensible as when it came to be made and exposed in the 

 open air. 



June the gth, about 5 in the morning, I repeated this experiment in an open 

 field, called the White Conduit, with much the same success as the former. 

 On shaking the bell before any air was intruded, it was but just audible at 30 

 yards distance. On the injection of one atmosphere, it became then as audible 

 at 6o yards, as it was before at 30. A second being intruded, the bell, on 

 shaking, might then be heard at go yards distance. But after that, though 

 near 100 strokes of the forcers were repeated, yet could it hardly be heard 20 

 yards farther. Which I attribute in a great measure to the reasons before 

 given. 



y/n Experiment made at a Meeting of the Royal Society, on the Diminution of 

 Sound in rarefied Air. By Mr, Fr. Hauksbee, N*^ 297, p. ]g04. 

 A bell being included under a receiver, which being shaken to make the 

 clapper strike, it was very observable that the interposition of the glass between 

 the bell and the ear, was a great obstruction to its sound, yet it was audible at 

 some good distance from it: but gradually withdrawing the air, and making 

 several stops to shake the bell at different degrees of rarefaction, the diminution 

 of the sound at every stop was very distinguishable. Till at last, when the 

 receiver was well exhausted of air, the remains of sound was then so little, that 



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