Section III, 1922 [213] Trans. R.S.C. 



A Method of Detecting Electrical and Magnetic Disturbances 

 By Brother Philip, M.A., F.S.C. 



(Presented by J. Patterson, F.R.S.C.) 



During the Worid War Professor J. C. McLennan, Ph.D., F.R.S., 

 of the University of Toronto, in the course of his investigations with 

 submarine cables, found induced in them stray currents which became 

 especially strong during thunder storms and which seemed to have a 

 directional effect. Pressure of other work prevented their being 

 investigated at the time; and at his suggestion, the present writer 

 undertook the investigation in colloboration with the Meteorological 

 Department, and under the direction of Mr. Patterson of that depart- 

 ment. The object was to record the various currents induced in a 

 coil of large diameter, to identify them, and, if possible, to correlate 

 them with meteorological, magnetic and other conditions. 



> Description of the Apparatus 



The apparatus consisted essentially of a long cable laid directly 

 on the ground around a nearly rectangular field, having a perimeter of 

 2,580 feet. The cable was formed from six strands of rubber insulated 

 copper wire enclosed in a lead sheath and connected to form a con- 

 tinuous circuit; a pair of leads, each 419 feet long, were brought to 

 the recording apparatus. Thus the total length of wire through which 

 the current passed was 16,318 feet, or about 3.09 miles. 



The house in which was kept the recording apparatus was mid- 

 way between the coil and the Toronto and York Radial line, and 

 450 feet from each. The leads connected to a galvanometer of the 

 Ayrton type with photographic registration and having a resistance 

 of 42.3 ohms, and figure of merit 5.4 by 10~^; the resistance of the 

 field coil was 55.65 ohms. To keep the deflections of the galvano- 

 meter on the scale a high resistance was used in series, so tTiat obser- 

 vations could be made either by the eye or automatically on bromide 

 film, 8 cms. wide. This film was fed by clock-work at the rate of 

 8 cms. an hour, when an automatic arrangement cut off the light for 

 a short time. 



Inside the photographic box was a stationary mirror to act as a 

 base line on the film. Both the mirrors were of focal length 50 cms. 

 so that the galvanometer deflections could be accurately estimated in 

 milliamperes. A deflection of 10 mms. on the film corresponded to 



