336 



TRANSACTIONS OP SECTION A. 



pressure was greatest, and that a resultant direction of N.-W. and S.-E. was 

 noticeable. 2 



A continuous daily curve nas now been completed for the past twelve years 

 from the E.-W. pendulum movements, and a two years' curve for the N.-S. 

 instrument. In studying these curves one detects the presence of certain pro- 

 nounced long period undulations possessing marked rhythmic characteristics too 

 great to be caused by local meteorological conditions. These and their probable 

 causes form the subject to be presented, while a detailed account of thei shorter 

 fluctuations will be described at a later date. 



In the following table the mean monthly and annual position of the E.-W. 

 pendulum from 1899 to 1910 is given : — 



Mean Monthly and Annual Position of E.-W. Horizontal Pendulum. 



(12 Years.) 



A cursory glance along curve E convinces one that there is a marked semi- 

 annual and annual movement throughout the twelve years presented. 



When studied in detail we find, beginning with January 1899, there is a 

 steady easterly swing until April, when until June a slight westerly movement 

 occurs, followed by a pronounced and rapid westerly swing continuing untilj 

 October, when, after two small easterly movements in November 1899 and! 

 January 1900, a westerly maximum is reached in February. This is followed! 

 in March by a pronounced eastward swing, followed throughout this year untiL' 

 November by a great westerly movement. Throughout the remainder of this; 

 curve the eastward movement reaches its maximum during the summer months., 

 and maximum west in winter. 



With respect to an annual movement, there is clearly to be seen a pre- 

 dominant westerly swing during 1899 and to November 1900, when an almost 

 equally strong force sets in in the opposite direction, and continues until the 

 summer of 1906, when a westerly tendency is shown for two years, followed 

 by an easterly progression which continues to 1910. 



Curve E', although for only the years 1909 and 1910, clearly indicates a. 

 southerly maximum movement about the time the easterly maximum occurs,, 

 while the extreme north movement is reached during the spring months- 

 Before attempting to account for these movements the following data bearing 

 upon other branches of this subject will be presented. 



The writer has classified all quakes recorded upon the Victoria seismograph 

 into two types, those originating within a radius of 1,000 miles of Victoria 

 termed ' B,' and all others originating beyond this 1,000 mile radius termed ' A.' 



The sum of ' A ' and ' B ' signifying all quakes recorded is represented 

 by curve ' C ' in fig. 1. 



This curve clearly shows a maximum number of quakes occurred between 

 September 1899 and January 1900, and another abnormal number is seen from 



3 ' The Effect of Atmospheric Pressure upon the Earth's Surface,' Royal 

 Astr. Soc. Can., 1908. A paper on the same subject was read at the British 

 Association Meeting at Winnipeg, 1909. 



