IN THE LAST HALF-CEjS t TURY. 19 



ter part of the eighteenth and the first de- 

 cade of the nineteenth century, of Her- 

 schel, of Laplace, of Young, of Fresnel, 

 of Oersted, of Cavendish, of Lavoisier, of 

 Davy, of Lamarck, of Cuvier, of Jussieu, 

 of Decandolle, of Werner and of Hutton, 

 suffices to indicate the strength of physi- 

 cal science in the age immediately preced- 

 ing that of which I have to treat. But of 

 which of these great men can it be said 

 that their labors were directed to practi- 

 cal ends \ I do not call to mind even an rarely 



t . -I directed 



invention of practical utility which we to prac- 

 owe to any of them, except the safety- em ] Sj 

 lamp of Davy. Werner certainly paid 

 attention to mining, and I have not for- 

 gotten James Watt. But, though some 

 of the most important of the improve- 

 ments by which Watt converted the 

 steam-engine, invented long before his 

 time, into the obedient slave of man, were 

 suggested and guided by his acquaintance 

 with scientific principles, his skill as a 



