84 THE ROYAL SOCIETY OF CANADA 



apparatus. With a makeshift "acoustic contact" to the bed rock it 

 was found possible by the use of a submarine microphone of the 

 carbon-granule type to detect the vibrations of the oscillator at 100 

 feet. It was concluded that by having the oscillator immersed in 

 water contained in a pit in the bed rock and employing hot-filament 

 amplifiers it would have been possible greatly to increase this distance. 



As a receiving microphone employed with an "audion" detector 

 as a sound amplifier, the oscillator proved to be very sensitive both to 

 sounds through air and to vibrations transmitted through earth 

 and rocks. 



Experiments were carried out with a carbon-granule microphone 

 specially designed to respond to vibrations transmitted through rock. 

 Sound produced by the blows of a pick could be heard very distinctly 

 from a distance of 200 feet, transmitted through bed rock. This type 

 of microphone when employed with the "audion" amplifier proved to 

 be extremely sensitive to sounds travelling in air. When placed 

 a few inches from the ground it was found capable of responding to 

 sounds inaudible directly by ear. 



Section 4. Experiments were carried out on the magnification of 

 telephonic currents by means of the hot-filament employed in wireless 

 telegraphy. 1 1 was found that by connecting the microphone or oscillator 

 into the primary circuit of a high-ratio transformer and a single-unit 

 De Forrest "audion" into the secondary, a very considerable magni- 

 fication was obtained in a pair of high-resistance telephone receivers. 



In conclusion the writers desire to express their thanks to Dr. 

 F. C. Harrison, Principal of Macdonald College, for the very kind 

 manner in which the facilities of the College Power House and Repair 

 Departments were placed at our disposal. 



McGill University, 

 July 27, 1917. 



