256 DETERMINATION OF THE ELEMENTS OF TERRESTRIAL 



esting account of the method employed for mapping the Tem- 

 agami iron ranges. Observations were made of both dip and 

 declination with the Thjilen-Tiberg magnetometer and the 

 formation was traced ov^r a distance of li miles, even through 

 swamps where there were no outcrops. In several places the 

 surface was stripped to confirm the observations. This work 

 and a more accurate survey of the north-east iron range were 

 carried on by Mr. Erik Nystrom, a.ssistant to Dr. Haanel, Sup- 

 intendent of Mines. The first account in English of Thulen's 

 method has been published this year at Ottawa by Dr. Eugene 

 Haanel.<i> 



Work of a Magnetic Savvey. 



Sufficient has been said to show the importance of mag- 

 netic surveys. With regard to the work of a complete survey, 

 it will be evident that three seperate undertakings are necessary, 

 first, the determination of the elements at a sufficient number of 

 stations properly situated to furnish reliable information over 

 the whole area ; second, the establishment of ' repeat' stations, 

 where the observations can be repeated from time to time so that 

 the secular changes may be noted ; and third, the establishment 

 of magnetic observatories so that the diurnal and annual changes 

 may be determined and non-periodic disturbances marked. These 

 observations, except in mining districts, would be of a temporary 

 nature, observations being taken at them only so long as the 

 surrounding district was being surveyed. In Germany such 

 observations have for many years been maintained at some of 

 the chief mines and in these are taken photographic records of 

 changes in the declination so that the mine surveyor may take 

 the exact value of the quantit}^ at the time he is running any line. 

 Several permanent observatories are also needed in Canada, and 

 one of these should be in a suitable position in these provinces. 

 The observatory at Toronto is the oldest^') in America, having been 



(1) On the Location and Examination of Magnetic Ore Deposits by Magnetometric 

 Measurements. by"Eugene Haanel, Ph. D. 



(2) The Gerard College Observatory, Philadelphia, was the first magnetic obserra 

 tory in America and was in operation from 1840-1845. 



