ON UNDERGROUND TEMPERATURE. 65 



which begins at nineteen miles from the shore and continues for fifteen 

 miles further. The slope of the land from the mines down to the shore is 

 about 1 in 40. The contour of the ground and the surface conditions in 

 the neighbourhood may therefore be regarded as normal. 



The leading authority on temperature gradient in this part of the 

 United States is Mr. Alfred C. Lane, the Michigan State Geologist. He 

 writes in 'Mineral Industry' (vol. iv. 1895, p. 767) : — 



' It is certain that, in the Lake Superior region, the rate of increase of 

 rock temperature is not far from 1° in 100 feet from a surface temperature 

 near 40°. For example, at 4,450 feet, the bottom of the North Tamerack 

 shaft, the rock is at 84° F.' 



Alluding to the preliminary announcement by Professor Alexander 

 Agassiz, president of the Calumet and Hecla Mining Company; of the 

 temperatures 59° F. at 105 feet, 79° F. at 4,580 feet, he says :— 



' Since at 105 feet the rock temperature should be near the mean 

 annual temperature of the locality, and since the mean annual temperature 

 of Calumet is, according to all isothermal maps, near 39°, and a mean 

 annual temperature of 59° is found somewhere near Tennessee, I do not 

 think we can safely assume a gradient very much less than 1° in 100 feet 

 after all.' 



President Agassiz's announcement appeared in the ' American Journal 

 of Science' for December 1895, p. 503, in the form of a preliminary 

 communication to the editors, with the statement : — 



' We propose when we reach our final depth, 4,900 feet, to take an 

 additional rock temperature, and then publish the full details of our 

 observations.' 



This depth was reached not long afterwards, the fact being recorded 

 in the ' Mining Journal ' for September 1896; but the promised details 

 have never been given to the public ; and a letter addressed by the 

 Secretary to Professor Agassiz in 1896 elicited the infoimation that the 

 rate of increase had turned out to be different from what it was believed 

 to be when the preliminary announcement was made. 



The evidence tendered in favour of the abnormally slow increase of 

 20° F. in 4,475 feet, or 1° in 224 feet, has thus been practically withdrawn. 

 Professor Hallock, writing in January last, says : — 



' The observation of temperature in the Calumet and Hecla mine, to 

 which you refer, is thoroughly discredited in this country.' 



With the view of probing the matter to the bottom. Professor Hallock 

 (on the suggestion of the Secretary) made arrangements for personally 

 exploring, in the spring and early summer, the temperature conditions of 

 the mines ; but in June he wrote : — 



' The Mining Company [the Tamarack Company], after having 

 promised me permission to make temperature observations, withdrew the 

 permission, and declined to permit me to enter the shaft.' 



The proposed trip was accordingly abandoned. Professor Hallock 

 has, however, sent large-scale maps and sections, and Mr. Lane has, at his 

 request, furnished information respecting underground temperature in 



1901. F 



