TRANSACTIONS OF SECTION A, 419 
moves towards the north, and when the easterly movement is pronounced 
the other instrument travels to the southward. 
Since the publication of these curves the author has succeeded in plotting 
a continuous daily record of the E-W pendulum from January 1, 1899, 
to December 31, 1908, a period of ten years, and has also made monthly and 
yearly tables therefrom. 
The following information has been gathered from the ten years’ study 
of this interesting subject :— 
The movements of these pendulums demonstrate a tilting of the earth’s 
surface in the direction where the atmospheric pressure is the greatest. For 
example, when the air pressure is greatest from California north-eastward 
to the Canadian prairie provinces, and lowest over British Columbia and 
the adjacent ocean, one pendulum swings towards the east and the other to 
the south. 
These movements are greatest during the stormy months of winter and 
least in summer, when the changes of air pressure are small throughout the 
Pacific slope. 
These pendulums often commence and continue to swing in a certain 
direction hours, and sometimes more than a day, before the barometers 
along the Pacific coast indicate the approach of great cyclonic and anti- 
cyclonic areas from the ocean. 
To arrive at the true connection of these pendulum movements and 
changes of air pressure, the former must be studied with the weather charts 
covering areas of from one to two thousand miles in extent, otherwise the 
local atmospheric conditions may appear to cause a tilting contrary to 
that indicated by the instruments. 
The loading of the Pacific slope during the winter months by heavy 
rains on the lower lands and vast quantities of snow upon the great 
mountain ranges of the interior may account for a small proportion of the 
easterly tilting. The ten years’ curves clearly demonstrate, however, that 
pronounced westerly swings occur when vast areas of high barometric pres- 
sure approach from the westward. 
The loading effect upon the coast due to a tidal action is only noticeable 
upon the records when little differences of air pressure prevail and during 
great tidal ranges. The remarkable absence of the tidal action is probably 
due to these instruments being situated upon the south end of Vancouver 
Island, where a fairly equal rise and fall of the tide occurs upon both sides 
of the island at about the same time. 
The diurnal range of a westerly swing in the morning and an eastward 
one in the evening is most marked during fine weather, and least when the 
weather is overcast. 
In order to obtain similar observations at other portions of the Pacific 
slope the author is pleased to state that Mr. T, 8. Shearman, our meteoro- 
logical observer at Vancouver, has at his own expense constructed two 
horizontal pendulums, and will shortly furnish daily readings from these 
instruments. 
Through the courtesy of the Chief Engineer of the Grand Trunk Pacific 
Company, of Prince Rupert, another instrument will shortly be installed 
there, and daily observations taken. 
Mr. T. R. Stockett, manager of a large coal mine at Nanaimo, has 
kindly consented to allow the author to install two instruments, one upon 
the surface and another 1200 feet below in this mine, and will furnish daily 
readings from them. ; 
These instruments the author is now personally constructing, and hopes 
to have all in operation before the great winter movements commence. 
In conclusion it is respectfully suggested that this subject be more fully 
studied by a special committee both upon this continent and at all stations 
where the Milne seismographs are installed. : 
EE 
