32 PROCEEDINGS OF THE CANADIAN INSTITUTE. 



close proximity to the magnetic instruments, and much time and labor have been 

 required to determine the precise effect of this ' ' iron mine ' ' on the various instru- 

 ments. It was not, however, until the autumn of 1892, when the trolleys began 

 to run, that we began to suspect that sooner or later the Magnetic Observatory 

 would have to be removed to another site. 



The magnetic instruments in the Observatory consisted of those brought out 

 by Lieutenant Riddell in 1840, of which eye readings have been taken six times 

 each day, and of another set of instruments, consisting of a bifilar for the measure- 

 ment of the horizontal component, and a balance needle for the vertical force, and 

 a declinometer, all of which record photographically. 



Electric cars first ran in Toronto on August 17th, 1892. The line first j)ut in 

 operation was that on Church Street, which was followed on September 5th, by 

 one on King Street, between George and Dufferin Streets. During the first few 

 weeks, while a very small vibration of the needle was discernible on the V. F. 

 curve, it was generally almost inappreciable, and it was not until September 20th 

 that the movement increased to an extent sufiicient to really impair the value of 

 our magnetic cvirves. A marked increase of current must have been used on that 

 day and afterwards. On October 10th the cars first ran on Yonge Street, and there 

 was only a very small increase in the vibration, but a decrease of about .000070 of 

 a dyne was observed when the current was on. 



About 10 a.m., January 14th, there was a marked increase of vibration, and 

 the vertical force increased about .000200 of one dyne. This disturbed period was 

 only temporary, and shortly after 5 p.m. on 'the 17th there was a reversal to the 

 smaller vibrations. This continued until May 15th, when larger vibrations began 

 again, and continued Avith varying intensity during the summer, while the decrease 

 of the vibration with the current ranged from about .000200 to .000500. This 

 disturbance was very great between September 12th and October 17th, and at 

 intervals during the following year ; bu.t there was no radical change in conditions 

 until December 17th, 1894, when a decrease of V.F., while the current was on, 

 was changed to an increase, this occurring when the cars first ran on McCaul St. 

 Throughout 1895 the vibration and amount of permanent deflection was very nearly 

 as it has been since ; but on October 15th, the increase of V.F. with the current 

 was again changed to a decrease, this occurring at the time that the railway com- 

 pany made certain changes in the feed wires. It is noticeable that, although 

 several changes occurred in the V.F., it at times having been less with the current 

 on and at other times greater, the horizontal force showed a decrease on all occa- 

 sions with the turn on of the current. This decrease during the past two years 

 was .000200 to .000500 of a dyne. No appreciable deflection of the declinometer 

 magnet was noted, the only effect being a continuous vibration, which rendered the 

 curves very ragged and difficult to read with accuracy. 



A study of the traces during the times that the various electric lines were 

 put in operation, showed that, with the currents ordinarily used, there was little 

 effect at three-quarters of a mile, and a further survey with a portable instrument 

 afforded further evidence in the same direction. 



Before definitely recommending that the Magnetic Observatory should be re- 

 moved from Toronto, the Director wrote to various well-known magneticians, present 

 at the meeting of the British Association in August, 1897, requesting the favovir of 

 their presence at the Observatory to inspect the photographic magnetic curves 

 there obtained with the View of expressing an opinion as to the advisability of 

 continuing the records at the present site, or of removal to some point distant from 

 electric tramways. Professor Riicker, F.R.S., Professor Carey Foster, F.R.S., 

 Professor Fitzgerald, F.R.S., Dr. Van Rijckevorsel, and Professor Frank Bigelow, 

 were the gentlemen who courteously accepted the invitation, and were pleased to 

 sign a statement that, in their opinion, the value of the magnetic observations at 

 Toronto had been seriously impaired by the trolley system, and advised removal 

 to some other site. 



It then having been decided to remove the Observatory, a point was chosen 

 nine miles northeast of the former Magnetic Observatory, latitude 43° 47^N., longi- 

 tude 79° 16^W. , easily accessible by railway, and yet very unlikely to be invaded 

 by the trolley system. At present there is no electric railway within seven miles, 

 and little prospect of one within five miles for many years. 



