ON MAGNETICAL AND METEOROLOGICAL OBSERVATIONS. 147 



altered in some respects to give it a degree of efficiency which it had not 

 before, and has been sent to Dr. Locke at Cincinnati, who has acknowledged 

 its receipt, which will in future be another station for the term observations. 



Magnetic Surveys and Itinerant Observations in progress, or about to be 



undertaken. 

 North American Survey. — The great interest which attaches to the survey 

 of the difficult and inhospitable country undertaken by Lieutenant Lefroy, 

 will render a sketch of his proceedings, so far as they are at present known, 

 especially acceptable. By letters written by him from York Fort in the 

 autumn, 'it appears that he had proceeded thence from the Lac de la Pluie, a 

 distance of about 500 miles, in the direct course towards the point of perpen- 

 dicular dip, during the whole of which journey he had found the total inten- 

 sity to diminish progressively. Later accounts have been very recently 

 received from him from Athabasca, where he was to pass the winter, and 

 whence he originally contemplated retracing his steps by a more inland route 

 to the lake above-mentioned on his way to Red River. 



At the date of those accounts Mr. Lefroy is making hourly observations 

 throughout the twenty-four hours, with one assistant, observing the changes 

 of the declination, the horizontal force, and the inclination, i. e. the declina- 

 tion and bifilar magnetometers, and the induction inclinometer. He will pro- 

 bably complete four or perhaps five months' hourly observations before 

 leaving Athabasca. After leaving, he says, 



" My plan is to go down to Mackenzie River in March on snow shoes ; 

 when there, there are two prospects, one is to return in May to Slave Lake, 

 and thence come here by the very first navigation, the other to Great Bear 

 Lake, and return with the Mackenzie River barges, which do not leave Fort 

 Simpson until near July. In either case the next step is to ascend Peace 

 River and cross by Lesser Slave .Lake, &c. to the Saskatchawan ; but if I 

 take the latter course I cannot expect to reach Red River before the very 

 end of September, which will endanger my return to Canada by open water, 

 and wholly preclude the idea of returning by Moose Factory. The latter is 

 not of much consequence, as if I return to this country it will be perfectly 

 easy to go by Moose and yet reach Lake Winnipeg in time for everything. 

 A little therefore will depend upon the seasons ; if the spring promises to be 

 a very early one and allows the Mackenzie River boats to come off before 

 their usual time, I shall perhaps venture on the latter ; at present I am most 

 inclined to the former. In either case I shall get a few weeks' transportable 

 observations in a more northern latitude, which is desirable." 



Arrived at Red River, he will find instructions to observe, if possible, the 

 decrement of magnetic intensity from its maximum in the Rainy Lake in a 

 westward direction, thus completing a system of lines radiating out from the 

 maximum in the northern, eastern and western directions (the eastern line 

 being already secured). Dr. Locke's observations, which are now printing 

 at Philadelphia, will furnish the fourth line. The full development of these 

 important features, which will establish in a very approximate manner the 

 central point of the isodynaraic ovals in this quarter, must await the assem- 

 blage and discussion of the whole mass of materials in process of collection*. 



* While this report is passing through the press, a letter, dated 22nd Nov., addressed by 

 Lieut. Lefroy to Capt. Sabine, announces his safe return to Toronto, having completed his 

 survey from the Slave Lake by Assiiiiboiu, Edmonton, down the Saskatcba\ran River to 

 Carlton and Cumberland, and thence by Norway House, Fort William, Sault S'" Marie and 

 Penetanguishene, to his entire satisfaction. A maximum of intensity occurs near the lake 

 of the woods. 



l2 



