Masterpieces of Science 



there is a dangerous opportunity for escape into 

 the sea, unless the current is of nicely adjusted 

 strength, and the insulator has been made and 

 laid with, the best-informed skill, the most con- 

 scientious care. In the constant tests required 

 in laying the first cables Lord Kelvin (then 

 Professor William Thomson) felt the need for 

 better designed and more sensitive galvano- 

 meters or current measurers. His great skill 

 both as a mathematician and a mechanician 

 created the existing instruments, which seem 

 beyond improvement. They serve not only in 

 commerce and manufacture, but in promoting 

 the strictly scientific work of the laboratory. 

 Now that electricity purifies copper as fire can- 

 not, the mathematician is able to treat his prob- 

 lems of long-distance transmission, of traction, 

 of machine design, with an economy and cer- 

 tainty impossible when his materials were not 

 simply impure, but impure in varying and in- 

 definite degrees. The factory and the work- 

 shop originally took their magneto-machines 

 from the experimental laboratory; they have re- 

 turned them remodelled beyond recognition as 

 dynamos and motors of almost ideal effective- 

 ness. 



A galvanometer actuated by a thermo-electric 

 pile furnishes much the most sensitive means 

 of detecting changes of temperature; hence elec- 

 tricity enables the physicist to study the phe- 

 nomena of heat with new ease and precision. It 

 was thus that Professor Tyndall conducted the 

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