534 Messrs. Wanklyn and Cooper on some new 



7 th. That whenever energy is transferred from one body to 

 another it is also always transformed from the potential to the 

 kinetic form, or vice versa. 



8th. That energy never changes its form without at the 

 same time being transferred from one body to another by an 

 act of work. 



9th (and most important). That the term " body" includes 

 every material thing, whether visible or ponderable or other- 

 wise, and that a piece of matter is to be regarded as a 

 different "hody" from the ultimate particles of which it is 

 composed ; so that when a bullet strikes a target one may 

 say that part of the energy of the bullet is transferred to its 

 particles; and when a spring uncoils suddenly, that the 

 .energy of the strained particles is transferred to the mass of 

 the spring — -just as easily as one may say that, when a pendu- 

 lum swings, energy is transferred from one " hody" the 

 gravitation medium, to another, the bob of the pendulum, or 

 vice versa, at every quarter swing. 



LXX. On some new Aparatus for use in Gas-analysis. 

 By J. Alfred Wanklyn and W. J. Coopek*. 



npHE analysis of gases by means of measurements over 

 -»- mercury has been brought to a state of great perfection, 

 and is admirably adapted for many purposes. Still there are 

 instances in which this method of procedure is inapplicable. 



Such instances are found in those cases where the con- 

 stituent is very small in amount, or where the gas attacks 

 mercury. There is a very familiar example in the carbonic 

 acid of the atmosphere. Ten thousand volumes of air contain 

 about four volumes of carbonic acid. If the chemist makes 

 a measurement of air confined over mercury, and then ab- 

 sorbs the carbonic acid by potash, and then measures the air 

 freed from carbonic acid, he obtains data from which he 

 might propose to calculate the amount of carbonic acid in the 

 air. But, as has been pointed out on various occasions by 

 different chemists, these data lose their value because the 

 experimental error is almost as large as the difference between 

 the two gas-measurements. Determinations of the carbonic 

 acid in atmospheric air carried out by this method are illusory; 

 and long ago (so long ago as the beginning of the century) 

 another method was resorted to. 



The other method consists in exposing a known volume of 

 air to the action of lime-water or baryta-water, and in noting 



* Communicated by the Authors. 



