iGOi ON THE SONIFEROUS VIBRATIONS OF TH2 GASSfeS. 



**'P** The organ-pipe em.iloyed is of the land called the stopped 



diapason: its width is O'SJ of an inch, depth 07 1, and its length, 

 without the plug by which it is tuned, 515 ;— the thickness 



Its pitch. of it? sides 15, and the width of the mouth 0'l6. When 

 tuned a minor tone above one of Hawkins's new C tuning- 

 forks, the length of the vibrating column of air was found to 

 be 4-1 inches j the barometer being at 29-60, and F. thermo- 

 meter at 65°. 



Air pump and A long barometer-gauge was added to the air-pump, having 



^"*^^" a scale movable by an endless screw for adjusting the zero to 



the surface of the mercury in the basin below it. In noting the 

 experiments, the height of the mercury in the gauge was sub- 

 tracted from that of a barometer suspended in the same room. 



Thermometer. Having by accident broken the small thermometer attached to 

 the bellows-frame, we registered the temperature from another 



Receiver. thermometer placed outside of the receiver. The capacity of 

 the glass receiver is 275 cubic inches, and that of the effective 

 part of the pump barrel 20 7. Nothing but pomatum was 

 used between the brass plates and the receiver, on account of 

 wetted or oiled leathers being known to afford a great deal of 



Vapour. vapour. Notwithstanding this, the gauge was depressed by 



vapour } for, on exhausting the receiver, the gauge indicated 



Exhaustion. two tenths of an inch less than the barometer, but when again 

 exhausted, after placing a cup with sulphuric acid in the re- 

 ceiver, the difference of the two v/as only OO6, and in one case 



usea to absorb ^^'® could perceive no difference. For this reason, in all theexpe- 



Tapour. riments, except those on water, alcohol, ether, and oil of tur- 



pentine, a glass containing five or six ounces of sulphuric acid 

 was placed by the bellows in the receiver. "With this pump, 

 and using the acid instead of muriate of lime, water has been 



I'f! produced ff^^zen by Mr, Leslie's process in two minutes, while the ther- 



•n 2'. mometer in the room was at 6/°. 



pjjjj^ Plate V fig. 1 (opposite page 240 of the present volume) 



represents the apparatus made use of for transferring liquids 

 into the exhausted receiver. It consists of a small glass tube, 

 graduated, which screws on the cock above the transfer-plate : 

 the top of this tube is closed by a piece of ground glass smeared 

 with pomatum. To the other end of the cock, under ths 

 plate, a small semisph«rical brass dish is screwed, to catch any 



liquii. 



