112 HEAT OR CALORIC. 



into alcohol, a portion of this fluid enters, as the air within contracts 

 by returning to its previous temperature. The liquid, thus introdu- 

 ced, is to be boiled in the bulb which has no beak, until the whole cav- 

 ity of the tube, and of both bulbs not occupied by liquid alcohol, is 

 filled with its vapor." 



" While in this situation, the end of the beak is to be sealed, by 

 fusing it in a flame excited by a blow pipe." 



"As soon as the instrument becomes cold, the vapor which had 

 filled the space within it, vacant of alcohol in the liquid form, is con- 

 densed, and a vacuum is produced ; excepting a slight portion .of va- 

 por, which is always emitted by liquids when relieved from atmos- 

 pheric pressure." 



"The instrument, thus formed, has been called a palm glass ; be- 

 cause die phenomena, which it displays, are seen by holding one of 

 the bulbs, in the palm of one of the hands." 



"When thus situated, the bulb in the hand being lowermost, an 

 appearance of ebullition always ensues in the bulb, exposed to 

 view, in consequence of the liquid, or alcoholic vapor, being pro- 

 pelled into it from the other bulb subjected to the warmth of the hand." 



" This phenomenon is analogous to the case of ebullition in vacuo, 

 or the culinary paradox ; but the motive for referring to the experi- 

 ment here, is to state, that as soon as the last of the liquid is forced 

 from the bulb, in the hand, a very striking sensation of cold, is expe- 

 rienced by the operator." 



"This cold is produced by the increased capacity of the residual 

 vapor for caloric, in consequence of its attenuation." 



Remark. 



A little ether dropped on either of the balls, immediately produces 

 a rush of the fluid into that ball, and the other ball being then treated 

 in a similar manner, the fluid as rapidly returns. The appearance of 

 ebullition in the palm or pulse glass is evidently much increased by 

 the fact that the thin film of fluid, lining the upper part of the ball, to 

 which the hand is applied, is rapidly converted into vapor, drives the 

 fluid before it, and then rushes through it ; that there is no ebullition 

 of the mass of the fluid, is proved by the fact, that if w r e reverse the 

 position of the ball, placing it uppermost, and allow the fluid .to rest 

 in the palm of the hand it remains entirely quiet. 



8. Cold consequent to a relaxation of pressure. 



" It is immaterial whether a diminution of density, arise from re- 

 lieving condensed air from compression, or from subjecting air of the 

 ordinary density to rarefaction. A cloud similar to that which has 

 been described as arising in a receiver partially exhausted, may usu- 

 ally be observed in the neck' of a bottle recently uncorked, in which 

 a quantity of gas has been evolved in a state of condensation by a 

 fermenting liquor." 



