No. IV.] 



REMARKS ON TABLE, No. VII. 



635 



taming any observations for variation in crossing the Barren Grounds, when the 

 expedition, on its return from the sea-coast, was passing over the same parallels of 

 latitude, and much to the eastward of the Copper-Mine River, because azimuths 

 obtained on that journey would have materially assisted in forming an estimate 

 respecting these curves. I apprehend much of the irregularity in the results of the 

 observations for the variation along the Copper-Mine River is to be attributed to 

 local causes of attraction, and particularly to the existence of iron ore among the 

 rocks, which is very general. 



As we proceeded along the sea-coast to the eastward from the mouth of the 

 Copper-Mine River to Bathurst's Inlet, the easterly variation decreased considerably, 

 though there was not a material change in the latitude ; but, in advancing to the 

 north and westward from Bathurst's Inlet to Point Turnagain, the easterly variation 

 increased again. 



A greater intermixture of iron ore was perceived in the rocks on the sea-coast, 

 than on the banks of the Copper-Mine River. 



It should be observed that when we were at the first cascade in Hood's River on 

 July 31st, we perceived the needles to traverse so sluggishly that it became neces- 

 sary to retouch them with the magnets. 



The remarks on the dip of the magnetic needle will accompany the Table which 

 contains those observations. 



4 m 2 



