ON VENTRILOQUISM. 247 



The weight of clouds, Sauflure eftimates at one-third or clouds weigh 



one-fourth of that of the cubic foot of air in which they fub- ^ one *j*f 



ot the air they 

 fjft. Hygrometer, p. 270. When the barometer rifes, clouds fl oat j n . 



are partly diflblved, a* denfe air is a better folvent than rarer 



air, and partly rife higher in confequence of the increafed 



fpecific gravity of the inferior air ; when the barometer falls 



the contrary takes place. 



VI. 



Experiments and Obfervations infupport of that Theory of Ven- 

 triloquifm uhich is founded on the Rtfle&ion of Sound. In a 

 Letter from Mr. John Gough. 



To Mr. NICHOLSON. 

 S I R, 



JL OU have given a fliort but comprehenfive yiew of my whether the 

 theory of ventnloquifm, at page 202, of the fourth volume ofphenomenon of 

 your Journal ; after which, you obferve, that the raani^ftfeferabletoe'cho? 

 difficulty of managing the echos of a room renders my ex- 

 planation of the phenomenon doubtful. In order to examine 

 the force of this objection experimentally, I proceeded in the 

 following manner: perhaps the inftruments which were ufed 

 on the occafion, may be deemed childifh by many of your 

 readers ; but a genuine friend to phyfical inquiry looks for 

 the event pi' an experiment, and does not regard the appear* 

 ance of the apparatus. 



Exp. 1. I took the (hell of a cocoa-nut, one end ofgxp. i. The 

 which had been cut off, fo as to make it an aperture, fome- be ats of a watch 

 thing more than two inches in diameter : after lining this with c hUfl?in one 

 woollen cloth, I put a watch into it, and furrounded the direction. This 



whole with a pillow in a manner, that left no part of the fhell ftron | e * found 



r v was then re- 



in contact with the atmoiphere, except the open end. When flexed by a no- 

 things were thus prepared, the pillow was placed upon my ta,,lc * urracc and 

 ii • ii r , . r , . was referred to 



knees, having the mouth of the nut turned from me : I then its laft direclioju 



liftened tp the foupd of the watch, fitting in an ered pofture, 

 and obferved it to be weak, but diftincl as to direction : a 

 circular metal tray, one foot in diameter, was held up before 

 my face, in the next place, and at the diftance of two feet 

 from it; upon which, the clicking of the watch grew much 



ftronger, 



