IN THE LAST HALF-CENTURY. 105 



epoch. To it also appertain the practical 

 execution and the working out of the 

 results of the great international system 

 of observations on terrestrial magnetism, 

 suggested by Humboldt in 1836 ; and the 

 invention of instruments of infinite deli- 

 cacy and precision for the quantitative de- 

 termination of electrical phenomena. The 

 voltaic battery has received vast improve- 

 ments ; while the invention of magneto- 

 electric engines and of improved means of 

 producing ordinary electricity has pro- 

 vided sources of electrical energy vastly 

 superior to any before extant in power, 

 and far more convenient for use. 



It is perhaps this branch of physical 

 science which may claim the palm for its 

 practical fruits, no less than for the aid 

 which it has furnished to the investigation 

 of other parts of the field of physical sci- 

 ence. The idea of the practicability of es- 

 tablishing a communication between dis- 

 tant points, by means of electricity, could 



