liv REPORT — 18G5. 



masses of matter, and the extinction of their motion on the surface of the 

 luminary. By calculations of the same order, depending on the rate of radi- 

 ation of heat into space, the past antiquity of the earth and the future 

 duration of sunshine have heen expressed in thousands or millions of centu- 

 ries *. In like manner the physical changes on the sun's disk, by which 

 portions of his darkly heated body become visible through the luminous 

 photosphere, have been connected, if not distinctly as a cause, certainly as a 

 coincident phenomenon, with particular magnetic disturbances on the surface 

 of the earth; the solar spots and the magnetic deflections concurring in 

 periods of maxima and minima of ten or eleven years' duration. Thus even 

 these aberrant phenomena become part of that amazing system of periodical 

 variation which Sabine and his fellow-labourers, British, French, German, 

 Russian, and American, have established by contemporaneous observation over 

 a large part of the globe t. 



With every change in the aspect and position of the sun, with every alte- 

 ration in the place and attitude of the moon, with every passing hour, the 

 magnetism of the earth submits to regular and calculable deviation. Through 

 the substance of the ground, and across the world of waters. Nature, ever 

 the beneficent guide to Science, has conveyed her messages and executed her 

 purposes, by the electric current, before the discovery of Oersted and the 

 magical inventions of "Wheatstone revealed the secret of her work. 



Even radiant light in the language of the new Philosophy is conceived of 

 by Maxwell J as a form of electro-magnetic motion. And thus the impon- 

 derable, all-pervading powers, by which molecular energy is excited and 

 exchanged, are gathered into the one idea of restless activity among the 

 particles of matter : — 



. . . seterno percita niotu : 



ever-moving and being moved, elements of a system of perpetual change in 

 every part, and constant preservation of the whole. 



What message comes to us with the light which springs from the distant 

 stars, and shoots through the depths of space to fall upon the earth after 

 tens, or hundreds, or thousands of years ? It is a message from the very 

 birthplace of light, and tells us what are the elementary substances which 

 have influenced the refraction of the ray. Spectral analysis, that new and 

 powerful instrument of chemical research for which we arc indebted to 

 Kirchhoff, has been taught by our countrymen to scrutinize not only planets 

 and stars, but even to reveal the constitution of the nebula?, those mysterious 

 masses out of which it has been thought new suns and planets might be 

 evolved — nursing-mothers of the stars. For a time, indeed, the resolution 



* Professor Thomson assigns to the sun's heat, supposing it to be maintained by 

 the appulse of masses of matter, a limit of 300,000 years ; and to the period of cooling of 

 the earth from universal fusion to its actual state, 98 million years. These are the lowest 

 estimates sanctioned by any mathematician. 



t A m ong the interesting researches which have been undertaken on the subject of the 

 spots, may be mentioned those of Wolf (Comptes Kendus, 1859), who finds the number 

 and periodicity of the spots to be dependent on the position of Venus, the Earth, Jupiter, 

 and Saturn. Stewart has made a special study of the relation of the spots to the path of 

 Venus (Proc. of the Koy. Soc. 186-1) ; and Cliacornac is now engaged iu unfolding his 

 conception of the spots as the visible effect of volcanic excitement. The peculiar features 

 of the solar surface are under examination by these and other good observers ; such as 

 Dawes, Nasmyth, Secchi, Stone, Fletcher, Howlett, and Lockyer. 



| Proc. of Eoy. Soc. 1864. The elder Herschel appears to have regarded the light of 

 the sun and of the fixed stars as perhaps the effect of an electro-magnetic process — a per- 

 petual aurora. 



