JULIUS ROBERT MAYER. 403 



six thousand times the "weight of the earth of solid coal. "With the quickness of 

 genius he saw that we had here a power sufficient to produce the enormous tem- 

 perature of the sun, and also to account for the primal molten condition of our 

 own planet. Mayer shows the utter inadequacy of chemical forces, as we know 

 them, to produce or maintain the solar temperature. He shows that were the 

 sun a lump of coal it would he utterly consumed in five thousand years. He 

 shows the difficulties attending the assumption that the sun is a cooling body; 

 for, supposing it to possess even the high specific heat of water, its temperature 

 would fall 15,000 in five thousand years. He finally concludes that the light 

 and heat of the sun are maintained by the constant impact of meteoric matter. 

 I never ventured an opinion as to the truth of this theory ; that is a question 

 which may still have to be fought out. But I refer to it as an illustration of the 

 force of genius with which Mayer followed the mechanical theory of heat 

 through all its applications. Whether the meteoric theory be a matter of fact or 

 not, with him abides the honor of proving to demonstration that the light and 

 heat of suns and stars may be originated and maintained by the collisions of 

 cold planetary matter. 



Let us now go back ten years and see how this verdict was ar- 

 rived at. 



When Professor Tyndall was preparing his work on heat, he desired 

 to acquaint himself with all that Mayer had done upon this subject. 

 He accordingly wrote to two eminent Germans, authorities upon this 

 question, for information. Both responded, and one of them, Professor 

 Clausius, procured Mayer's publications to send to Tyndall. In his 

 first letter he said he thought Professor Tyndall would not find any- 

 thing very important in Mayer's writings. But before forwarding the 

 memoirs he read them himself, and then wrote to Tyndall : " I must 

 here retract the statement, in my last letter, that you would not find 

 much matter of importance in Mayer's writings ; I am astonished at 

 the multitude of beautiful and correct thoughts which they contain." 

 He then went on to point out various important subjects in the treat- 

 ment of which Mayer had anticipated other eminent writers. Professor 

 Tyndall perfectly agreed with Clausius, and resolved to do his share 

 toward making so able and original a man better known in England. 

 Accordingly, on June 6, 18G2, he gave a most interesting lecture at 

 the Royal Institution, full of new views and novel experiments, on 

 the subject of " Force." At its close he remarked : " To whom, then, 

 are we indebted for the striking generalizations of this evening's dis- 

 course ? All that I have laid before you is the work of a man of whom 

 you have scarcely ever heard. All that I have brought before you has 

 been taken from the labors of a German physician, named Mayer. With- 

 out external stimulus, and pursuing his profession as town physician 

 in Heilbronn, this man was the first to raise the conception of the in- 

 teraction of natural forces to clearness in his own mind. And yet he 

 is scarcely ever heard of in scientific lectures, and even fco scientific 

 men his merits are but partially known. Led by his own beautiful 

 researches, and quite independent of Mayer, Mr. Joule published his 



