3(36 CAPILLARY ATTRACTION, ETC. [MEMOIR XXVI. 



structures, far from being the products of one such homo- 

 geneous power, are rather the resultants of the action 

 of a multitude of material forces. Gravity, cohesion, 

 elasticity, the agency of the imponderables, and all other 

 powers which operate both on masses and atoms, are 

 called into action, and hence it is that the very evolution 

 of a living form depends on the condition that all these 

 various agents conspire. Organized beings and organ- 

 ized bodies spring forth in those positions only to which 

 the rays of the sun have access. They are, therefore, 

 limited to the atmosphere, the sea, and the surface of the 

 earth. 



If we expose some spring -water to the sunshine, 

 though it may have been clear and transparent at first, 

 it presently begins to assume a greenish tint, and after a 

 while flocks of green matter collect on the sides of the 

 vessel in which it is contained. On these flocks, when- 

 ever the sun is shining, bubbles of gas may be seen, 

 which, if collected, prove to be a mixture of oxygen and 

 nitrogen, their proportion being variable. Meantime 

 the green matter rapidly grows, its new parts, as they 

 are developed, being all day long covered with air- bells, 

 which disappear as soon as the sun is set. If these ob- 

 servations be made on a stream of water the current of 

 which runs slowly, it will be found that the green mat- 

 ter serves as food for thousands of aquatic insects which 

 make their habitations in it. These insects are indued 

 with powers of rapid locomotion, and possess a highly 

 organized structure. In their turn they fall a prey to 

 the fishes which frequent such streams. 



Thus by the influence of the sunlight organic matter 

 is added to vegetable systems, the action being accom- 

 panied by a variety of chemical decompositions and in- 

 terstitial diffusions. The substances arising are such as 

 are necessary for the uses of the plant ; and in order to 



