AMOUNT OF FORCE IN THE SOLAR RADIATIONS. 



77 



state. Thrown out from the mechanism, after their office is over, they leave behind 

 them marks of the changes through which they have passed, and of the facts to which 

 they have given birth, and thus stand at last in connexion with events to which at first 

 they were not apparently allied. 



286. From the combustion of small quantities of carbon, we see, in improved steam- 

 engines, how great an amount of force can be originated, and by the oxydation of a few 

 grains of zinc in voltaic batteries, what surprising chemical results arise. From those 

 more ordinary cases of changes accomplished by the action of light, which appear to 

 be feeble and slowly produced, we should form the most erroneous opinions of the force 

 of the sun rays. General considerations might lead us to know that the principle 

 which has in charge the keeping up of the constitution of the atmosphere, and regula- 

 ting the vital functions of plants, is of great intensity. Thus, I have found that the 

 rays which are emitted from a common wax candle are superior in chemical force to 

 the current which is evolved by a cell of Grove's battery, the most powerful of voltaic 

 combinations known, for they could effect the recomposition of muriatic acid much 

 faster than the battery could decompose it, and yet that battery was found competent 

 to maintain a platina wire white hot, and, if the views of Dr. FARADAY are correct, was 

 evolving more electricity than is developed by any thunder storm. If this is the case 

 with a candle, what, then, shall we say of brilliant rays of the sun, which impinge on the 

 earth on all sides ? 



287. That force, therefore, the mode of action of which we are now to discuss, is 

 far from an insignificant power in Nature. In generality and intensity it rivals any that 

 is known ; in interest it is superior to them all, for it stands in connexion with organiza- 

 tion and living things. 



288. Even after having undergone that enormous reduction of intensity which must 

 take place in reflexion from the surface of the moon, the solar rays still act with energy; 

 for the moonshine produces all kinds of decompositions, acting like the sunbeam, 

 though in a feeble way, being probablv reduced to J^VTCT part of its original power (Ap., 

 545). 



289. This force, thus affecting in a radiant form vegetable organizations, produces 

 .he results we are studying. The idea commonly entertained of its feebleness is utterly 

 inaccurate and wrong. 



290. In proceeding now with the more immediate object of this chapter, I shall 

 follow the course of thought which has presented itself in my experiments. At the 

 risk of dwelling somewhat in tedious detail, I shall also describe the different experi- 

 ments from which the final arguments are drawn ; and as it will be found that the 

 rays of light and the tithonic rays are eventually under the government of the same 

 laws, similar expressions including the phenomena of both, I shall commence with giving 

 the theory of the absorption of the tithonic rays first, and then show how tne same 

 theory includes the phenomena of light. This leads naturally to a division of the sub- 

 ject under two heads. 



I. Theory of absorption of the tithonic rays. 



II. Theory of ideal coloration. 



