146 SPEED OF ELECTRIC ACTION. 



VARIED VELOCITIES IN THE TRANSMISSION OF ME- 

 CHANICAL ACTION. 



* 



Vibration of light transmitted through the 

 electric ether in infinite space is found to be 

 about 190,000 miles per second, being nearly 

 1,000,000,000 feet per second. 



The velocity of vibrations of sounds in air . . 1,150 feet per second. 



in water . 4,160 



in wood . 12,000 



iron wire . 15,000 



The velocity of transmission of currents in 

 closed circuits, through short wires of a large size, 

 is nearly the same as that of light. The velocity 

 is greatly diminished in passing through ordinary 

 telegraph wires. The diminution is nearly in the 

 ratio of the squares of the increased distances, 

 and inversely as the size of the conductor. With 

 a fine wire the current is not only interrupted, 

 but molecular vibrations are produced so intense 

 as to disintegrate the wire itself. 



It appears, by experiments made by Mr. Walker 

 of the United States Coast Survey, that the velocity 

 of the transmission of electric currents between a 

 telegraph station in Cambridge, Mass., and Phila- 

 delphia, was about 18,700 miles per second. 

 Others have calculated a higher velocity. " A 

 communication by telegraph between Bombay and 

 London has been made and answered in thirty- 

 three seconds." " A perceptible portion of a 

 second is occupied in transmitting a telegraphic 

 signal across the Atlantic." 



