a06 ROYAL SOCIETY OF CANADA 



N-E-S-W direction. The greater part of the Gulf is less tihan 100 

 fathoms deep. 



'The object of the examination of those mareograms was to examine 

 the secondary oscillations, which one finds superposed on the regular 

 tidal movements, and to see if any relationship exists between the occur- 

 rence and intensity of these secondary oscillations and the microseisms 

 registered at Ottawa. — For the study of the oscilhitions of the Gulf, the 

 mareograms of St. Paul seemed the most suitable. 



Secondary oscillations have received considerable attention by 

 various investigators, but so far without conclusive proof of the cause of 

 their origin. — Last year the Earthquake Investigation Committee of 

 Japan published a report on " The Secondary Oscillations of Ocean 

 Tides." In the investigations " Professor Omori was led to the conclu- 

 sion that the bays or inlets oscillate like fluid pendulums with periods 

 peculiar to their own."' 



Eecords were obtained from many bays about the Japanese coast by 

 specially designed portable tide-gauges and the results tabulated. The 

 period of oscillation was computed by the formula 



ii 



I g h where I = length of bay, h = mean depth, and g = 



acceleration. The denominator represents the velocity of the long 

 wave. 



The observed and calculated periods, although varying for different 

 bays very widely, from 9™ to 363™, agree pretty well throughout. This 

 part of the investigation seems to show conclusively that each bay has 

 its own inherent period or note like a tuning fork and will oscillate with 

 its own period, " if it be excited by waves in the external sea having the 

 synchronizing component." From this it would follow that we can get 

 little or no information about the period of the microseisms as dependent 

 upon the periods of the bays, for microseisms with the sam|e period 

 obtain over very large areas, tens or hundreds of thousands of square 

 kilometres in extent. — However "as to the cause of the long waves 

 which manifest themselves as secondary undulations " the above report 

 says, " we may mention the wind, the cyclone, the earthquake, etc." 

 In short, the report does not show that the change of atmospheric pres- 

 sure is the direct cause of these secondary oscillations and is indicated 

 by them. 



Coming now to the mareograms of St. Paul Island, it is found that 



(1) Secondary oscillations are always present throughout the year, 



(2) The range or double amplitude varies; being greater in winter 

 than in summer. The range running from 1 cm. to 30 cm. 



