PREFACE TO THE ENGLISH EDITION 



IN the historical record of science the name of Helm- 



holtz stands unique in grandeur, as a master and leader 



in mathematics, and in biology, and in physics. His 



admirable theory of vortex rings is one of the most 



beautiful of all the beautiful pieces of mathematical 



work hitherto done in the dynamics of incompressible 



fluids. In 1843, when he was only twenty-two years 



old, and barely emerged from his undergraduate course 



as a medical student, he showed, in his first published 



scientific paper, a clear appreciation of the necessity 



of distinguishing vital from non-vital phenomena : and 



he gave experimental evidence tending to prove that 



putrefaction and fermentation are essentially vital 



actions : and thus led the way to Pasteur's splendid 



and beneficent discoveries. His Erhaltung der Kraft, 



published in 1847, was a guide to his own countrymen, 



and to the rest of the world, in the doctrine of energy 



through the whole range of dynamic action in dead 



and living matter, then despised and rejected by nearly 



all the high priests of science ; now cherished by all 



as a most fruitful result of modern research. His 



Tonempfindungen, and his Physiological Optics, are 



not mere textbooks : they are ever memorable Prineipia 



of the perception of sound, and of light, by living 



creatures. 





