10 THE BEGINNINGS OF LIFE. 



the recently published third edition of his c Correlation 

 of the Physical Forces,' he says, c As far as I am now 

 aware, the theory that the so-called imponderables are 

 affections of ordinary matter, that they are resolvable 

 into motion, that they are to be regarded in their 

 action on matter as forces, and not as specif c entities, 

 and that they are capable of mutual reaction, thence 

 alternately acting as cause and effect, had not at that 

 time been publicly advanced.' But it was also in the 

 year 1 842, though in its latter part, that Dr. Mayer \ 

 a physician of Heilbronn, announced independently 

 a doctrine substantially similar, to the effect that the 

 imponderables were forces at once indestructible and 

 convertible. He actually calculated the mechanical 

 equivalent of heat out of data derived from the velocity 

 of sound in air-r-an intellectual feat only possible to 

 a man of rare originality. Professor Tyndall says 2 of 

 him, c When we consider the circumstances of Mayer's 

 life, and the period at which he wrote, we cannot fail 

 to be struck with astonishment at what he has ac- 

 complished. Here was a man of genius working in 

 silence, animated solely by a love of his subject, and 

 arriving at the most important results some time in 

 advance of those whose lives were entirely devoted 

 to Natural Philosophy. It was the accident of bleeding 

 a feverish patient at Java, in 1 840, that led Mayer to 



Bemerkungen iiber die Krafte der umbeleten Natur,' Liebig's 

 Annalen, 1842, vol. xlii. 

 8 Loc. cit. p. 445. 



