150 ANNUAL OF SCIENTIFIC DISCOVER Y. 



SPECIFIC INFLUENCE OF THE COLORED KAYS OF LIGHT. 



M. Baudrimont gives, as the result of his researches upon the chem- 

 ical action of solarlight, that, contrary to the opinion generally enter- 

 tained, chemical rays exist throughout the whole extent of the solar 

 spectrum. The facts observed also lead to the belief that each species 

 of colored light possesses a special action, and that each may be com- 

 pletely inert with regard to certain matters, but, on the contrary, 

 very energetic with respect to others. Another series of experiments 

 enables M. Baudrimont to establish the influence of the various colors 

 of the spectrum upon the development of vegetation. Thus, for in- 

 stance, no colored light permits vegetables to go through all the phases 

 of their evolutions ; none of them have flowered or fructified. Violet- 

 colored light is positively injurious to plants : they absolutely require 

 white light. Paris COD: of the Photographic News. 



PHYSICAL CONSIDERATIONS REGARDING THE POSSIBLE AGE 



OF THE SUN'S HEAT. 



In a paper on tli3 above subject, presented to the British Associa- 

 tion (1861) by Prof. TV. Thomson, the author prefaced his remarks 

 by drawing attention to some principles previously established. It is 

 a principle of irreversible action in nature, that, " although mechani- 

 cal energy is indestructible, there is a universal tendency to its dissi- 

 pation, which produces gradual augmentation and diffusion of heat, 

 cessation of motion, and exhaustion of potential energy, through the 

 material universe." The result of this would be a state of universal 

 rest and death, if the universe were finite and left to obey existing 

 laws. But as no limit is known to the extent of matter, science points 

 rather to an endless progress through an endless space of action, in- 

 volving the transformation of potential energy through palpable motion 

 into heat, than to a single finite mechanism, running down like a clock 



' ^j d* 



and stopping forever. It is also impossible to conceive either the be- 

 ginning or the continuance of life without a creating and overruling 

 power. The author's object was to lay before the Section an applica- 

 tion of these general views to the discovery of probable limits to the 

 periods of time, past and future, during which the sun can be reck- 

 oned on as a source of heat and light. The subject was divided 

 under two heads : 1. On the secular cooling of the sun ; 2. On the 

 origin and total amount of the sun's heat. We do not know certainly 

 that the sun is losing any heat at all, and it is certain that some heat 

 is generated in its atmosphere by the influx of meteoric matter, and 

 it is possible that the amount thus generated is so balanced as to 

 compensate the loss by radiation. It is also possible that the sun is 

 now an incandescent liquid mass, radiating away heat either primi- 

 tively created or thus generated by the fallinof in of meteoric matter. 



* O / O 



From astronomical considerations, he showed that none of this matter 

 can come from space beyond the earth's orbit ; and by considerations 

 derived from the disturbances of the inferior planets and the zodiacal 

 light, the author had shown that.the amount of meteoric matter could 

 not be nearly enough to give a supply at the present rate for 300,000 



