2 THE POPULAR SCIENCE MONTHLY. 



of precision, had learned no other, and remained indifferent to a great 

 question to which the old methods did not apply. We are called into 

 existence by a great central fire, the sun, by which we continue to 

 exist from one hour to another. What is it ? what is this heat which 

 it pours into space, and wiih whose cessation we shall cease ? How 

 long will it continue to feed our lives ? A few years ago, with almost 

 the sole exceptions of the Herschels and Pouillet, no one even asked 

 these questions, much less intelligently sought their solution. 



It is hard to say to whom the awakening of attention is due ; yet 

 if any one were to be named, it should perhaps be the Italian physicist 

 Melloni, "the Newton of heat." 



His book, " La Thermochrose," has to me an attraction of its own, 

 for the author, with the ingenuous confidence of his nation, begins, 

 not by describing his thermopile or galvanometer, but by taking the 

 reader into his j^ei'sonal experience, and telling him how even as a 

 child he felt an invincible curiosity about what we have just seen 

 hardly any one else then cared for, and how, rising long before dawn, 

 he loved to seek some quiet spot, to wait there in the silence of the 

 sleeping world the first beams of the sun, and as he felt their warmth 

 and heard the stir of life they awakened round him, how he too was 

 stirred with wonder and interest as to the nature of that mysterious 

 thing, radiant heat, and resolved to give his future to its study. If to 

 distinguish a cause for wonder and inquiry in what to the common 

 mind has called for neither be a characteristic of genius, then Melloni 

 must be allowed its possession, and in his. but too short years he 

 showed the world how much interest and importance lay in this then 

 neglected stiidy, which so many with clearer knowledge and better 

 methods follow to-day. 



Fraunhofer's previous work had prepared the way for the spec- 

 troscope, and with the now awakened interest in these questions, its 

 employment by Kirchhoff in 1860 may be said to inaugurate the pres- 

 ent study of solar physics, as distinguished from the classic astronomy, 

 which concerned itself with number and measure first, and in a wholly 

 secondary degree with the physical characteristics of the heavenly 

 bodies. This study occupies itself with the former, indeed, but chiefly 

 in aid of other investigations, and by the study of solar physics then, 

 we mean much more than a telescopic examination of the sun ; we 

 mean besides this the analysis of its radiations by the spectroscope, 

 their summation by the photometer and thermopile, the determina- 

 tions of its heat and the possible effects of changes in it on teirestrial 

 meteorology, and generally the pursuit of all those problems which 

 unite the methods of physics and astronomy. 



In 1860 we already knew that the sun was surrounded by an en- 

 velope then visible only during total eclipses, and which was surmised 

 to be gaseous ; and of the sun itself we knew very little more than 

 that it was a hot globe with spots upon it ; for, though Schwabe had 



