434 THE SCIENTIFIC PAPERS OF 



2. That these gaseous compounds are capable of being dis- 

 sociated by radiant solar energy while in a state of extreme 

 attenuation. 



3. That these dissociated vapours are capable of being com- 

 pressed into the solar photosphere by a process of interchange with 

 an equal amount of reassociated vapours, this interchange being 

 effected by the centrifugal action of the sun itself. 



If these conditions could be substantiated, we should gain the 

 satisfaction that our solar system would no longer impress us with 

 the idea of prodigious waste through dissipation of energy into 

 space, but rather with that of well-ordered self-sustaining action, 

 capable of perpetuating solar radiation to the remotest future. 



"ON THE DEPENDENCE OF RADIATION ON 

 TEMPERATURE," 



BY SIR WILLIAM SIEMENS,* F.R.S., D.C.L., LL.D. 



SIR Isaac Newton held that the radiation of heat from a hot 

 body increased in arithmetical ratio with the difference of 

 temperature between it and the surrounding bodies. This law 

 forms a rough approximation to the truth over a very limited 

 range of temperature. MM. Dulong and Petit carried out an 

 elaborate experimental research on the rate of cooling of hot bodies 

 by radiation, extending to somewhat higher temperatures, and 

 deduced from their observations the empirical formula Rate of 

 cooling =ra(r0077y(l-0077 T -' 1). 



Here T is the temperature of the hot body in degrees Centigrade, 

 t the temperature of the surrounding matter, and m is a constant 

 depending on the nature of the radiating body. This formula 

 agrees very fairly with experimental results for ordinary tempera- 

 tures, but, like Newton's law, it has been shown that it cannot be 

 applied for a wider range. 



* Excerpt Proceedings of the Royal Society, Vol. XXXV. 1883, pp. 166-177. 



