MEMOIR XXVI.] CAPILLARY ATTRACTION, ETC. 355 



of the air increases with the impelling force. The mat- 

 ter to be moved is increased, therefore, in the same pro- 

 portion as the pressure, and therefore the final velocity 

 is the same, and the same takes place in the case of a 

 tissue which is compressing a gas. 



Such is the case while the gases are engaged with 

 each other in the tissue; but as soon as they pass from 

 it, the condensed gas, being no longer under its compres- 

 sion, expands freely, and, when measured, gives a result 

 differing from that which it would have been had not 

 the tissue compressed it. 



Accordingly, when carbonic acid and air are separated 

 by a screen of stucco, which absorbs each to a very small 

 extent, they diffuse, according to the law of the square 

 roots of their density, one volume of air replacing 0.8091 

 of carbonic acid, the volume on that side of the screen 

 where the carbonic acid was increasing in quantity. 

 But if a thin sheet of India-rubber be used as a screen, 

 since it can condense one atmosphere of carbonic acid 

 while it does not act upon the air, though the same rate 

 of exchange ensues, there is a diminution of the gaseous 

 matter on the side containing the acid, and one volume 

 of air replaces 1.6182 of the acid. 



In every plant two prominent operations are carried 

 forward: (1) the production of organic matter; (2) its 

 distribution through the various parts of the vegetable 

 system. 



In 1844 I published a work under the title of "A 

 Treatise on the Forces that Produce the Organization of 

 Plants." It \vas a monograph chiefly devoted to the il- 

 lustration or investigation of those operations, and com- 

 bated the existence of the Vital Force of physiologists 

 as a homogeneous and distinct power. 



The progress of science shows plainly that living 



