Miscellaneous Contributions by Dr. Hare. & 



small proportion of vapor, which is always emitted by liquids 

 when relieved from atmospheric pressure. 



The well known instrument, thus formed, has been called 

 a palm glass ; because the 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, expo- 

 sed to view, in consequence of the liquid, or alcoholic vapor, 

 being propelled 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 experiment here, is to advert to the fact, that as soon 

 as the last of the liquid is forced from the bulb, in the hand, 

 a very striking sensation of cold, is experienced by the ope- 

 rator. 



This cold is produced by the increased capacity of the re- 

 sidual vapor for caloric, in consequence of its attenuation. 

 The analogy is evident between this phenomenon and that 

 •above described, both being attributable to the increase of 

 capacity for caloric, resulting from a diminution of density. 



Relaxation of pressure. 



It is immaterial whether the diminution of density, arise 

 from relieving condensed air from compression, or from sub- 

 jecting air of the ordinary density to rarefaction. A cloud 

 similar to that which has been described as arising in a re- 

 ceiver partially exhausted, may usually be observed in the 

 neck of a bottle recently uncorked, in which, in consequence 

 of its generation by fermenting liquor, a quantity of gas has 

 been evolved disproportionable to the space. 



4. Apparatus for shewing that when pressure is relaxed the 

 capacity of air for heat and moisture is increased. 



This figure represents an instrument which I have employ- 

 ed to illustrate the influence of compression, on the capacity 

 of air for caloric and moisture. 



A glass vessel with a tubulure and a neck, has an air ther- 

 mometer fastened air tight by means of a cork into the one, 

 while a gum elastic bag is tied upon the other, as represented 

 in this figure. Before closing the bulb, the inside should be 



