1883.] 



On the Circumsolar Expedition to Fort Rae. 



175 



the garden attached to the Roman Catholic Mission, bnt for food the 

 inhabitants chiefly depend upon the produce of the nets, and on deer, 

 which are brought in by the Indian hunters attached to the post. 



On arrival it was found that the magnetic instruments required a 

 good deal of setting to rights, their boxes being tilled with water and 

 the fittings loosened, so that not a single instrument was quite in 

 working order. There was, moreover, no building ready for their 

 reception, so that it was not possible to keep the 31st August — 

 1st September as a term day, but we succeeded in getting the 

 meteorological instruments into position so as to commence observa- 

 tions with them at midnight on the 31st. 



We were fortunate in finding a building that admitted of con- 

 version into a magnetic observatory, it only requiring a floor, fire- 

 place, door and windows to be habitable. This work was at once 

 commenced, and on the 3rd September the declinometer, on the 4th 

 the bifilar, and on the 6th the vertical force magnetometer were 

 mounted in their places. This observatory was finished on the 10th 

 September, and another one commenced for astronomical and absolute 

 magnetic observations, the continual wind rendering out-door obser- 

 vations unsatisfactory. 



The men of my party were accommodated in the house of one of 

 the sub-officers of the fort, and I had a room in the house of the 

 Hudson's Bay Company's officer in charge. 



The instruments, on the whole, suffered but little from the journey. 

 One barometer and one thermometer were broken, and the object 

 glasses of the telescopes of most of the magnetic instruments were 

 nearly opaque, the cement joining the two lenses having from some 

 cause or other melted on the journey. Our provisions were more 

 damaged, 190 lbs. sugar, 30 lbs. of tea, all our rice, and most of our 

 baking powder having been destroyed. 



The observations were then carried on without interruption until 

 the 31st August, 1883. 



Magnetic Observations. 



The balance magnetometer was the only magnetic instrument 

 whose performance was not satisfactory, as not only did it frequently 

 get out of adjustment, but in times of magnetic disturbance it often 

 vibrated through so large an arc that exact reading was im- 

 possible. The other instruments were remarkably free from vibration, 

 and there was never any difficulty in reading them, but it was found 

 necessary to extend the scale of the bifilar on the side of decreasing 

 force, owing to the great movements of this instrument. 



The greatest magnetic disturbance was on the 17th, 18th, and 19th 

 November, 1882, when all the instruments moved at times beyond the 



