74 THE ROYAL SOCIETY OF CANADA 



surface. As regards its sensitiveness the author states: "The actual 

 sensibility (of the seismoscope) is very great, such, that resting on 

 solid granite a blow of a light hammer on the rock can be perceived 

 at 100 yards off, a stamp with the foot at 50 or 60 yards, and on 

 compact sand or clay, a horse trotting can be observed at a quarter 

 of a mile away." With this apparatus it was found possible to detect 

 the transmission of sound through such an unpromising medium as 

 wet sand at | mile from the source of disturbance caused by exploding 

 a cask containing 25 pounds of blasting powder buried at a depth of 

 6| feet. 



Shortly after the discovery of the microphone (about 1878) 

 suggestions were immediately put forward with respect to possible 

 important uses for this instrument. For instance, in an article' 

 in the English Mechanic of June 21st, 1878, some military and naval 

 applications are suggested. Although such applications do not appear 

 to have been based on experiment, the microphone was employed 

 about this time by seismologists in the study of earth tremors of 

 seismic origin. An account of experiments of this type by several 

 observers, notably by Italian seismologists of that period, is given by 

 Darwin.^ The evidence there discussed bears out the fact that 

 subterranean noises are capable of being propagated through solid 

 bed rock. More recent observations by means of extremely sensitive 

 modern seismographs indicate that very minute tremors (microseisms) 

 are being continually propagated through the earth's crust, and have 

 been observed by seismologists both in Europe and America. These 

 microseisms have a period of about 5 seconds and are regularly 

 observed at the Dominion Observatory, Ottawa. As a result of a 

 continuous study of the microseismograms, there is good reason to 

 believe that sources of disturbance giving rise to them are situated 

 on the shores of the Gulf of St. Lawrence and on the coasts of Nova 

 Scotia and New England, and that their occurrences synchronize 

 with the prevalence of high winds on these coasts: the succession of 

 sea-waves beating on the bluff rocky coasts of these neighbourhoods 

 is believed to be responsible for these disturbances, which apparently 

 are capable of travelling through the lower strata of bed rock for many 

 hundreds of miles and still retain sufhcient energy to make themselves 

 felt on a sensitive seismograph.'' 



'Quoted by Du Moncel in ''The Telephone, the Microphone and the Phonograph," 

 English Translation (Harper and Brothers, New York, 1879). 



-Darwin, Sir G., "Collected Works " Vol. 1, pp. 435 et seq. 



^Report of the Chief Astronomer, Dominion Observatory, Ottawa, 1011., pp. 

 26-27. 



