﻿at Lake Superior Copper Mines. 



127 





Thermal in- 





Distance be- 



Highest 





Mine 



crease in feet 



of mine 

 in feet. 



tween rating 



temperature 



Character of 



* 



for 1 degree 



stations in 



oi mine 



" Lode." 





Farenheit. 



feet. 



(Tarenheit). 





Atlantic 



99'5 



907- 



796- 



51-6° 



Melaphyre. 



Central 



101 



1950" 



I860- 



61- 



Fissure vein. 

 Quartz prophyry 



Conglomerate 



95- 



617. 



527- 



48-3 



Conglomerate. 



Osceola 



76'5 



996- 



860- 



54-5 



Melaphyre. 

 Quartz prophyry 



Tamarack 



(110 7) 



2240- 



2104- 



62- 



Conglomerate. 



Quincy 



122- 



1931- 



1820- 



58-5 



Melaphyre. 



Average . . 



100-8* 







Of these observations, those at the Atlantic mine were made 

 under very favorable circumstances and this particular rate of 

 practically 100 feet to 1°, was closely checked by other deter- 

 minations made on intermediate levels. In finding the rate for 

 this mine, as in all other cases, as great a distance as possible 

 was obtained between the two rating stations, while the upper 

 station was always taken so far below the surface as to be 

 beyond the influence of solar heat. The mine is about 2 miles 

 south of Portage Lake, which is a narrow, long arm of Lake 

 Superior. 



The Conglomerate mine is about 36 miles northeast of the 

 Atlantic mine, as measured along the formation, and like the 

 Atlantic at the southern end, is at the other extreme of the 

 series of mines examined, the others being between these two. 

 It is in a belt of conglomerate, and is 3 miles distant from the 

 shore of Lake Superior. 



The Central mine is on a narrow fissure vein and is about 2-J 

 miles distant from the Lake Superior shore line. 



The Osceola mine is nearly 5 miles from the western shore 

 line of Lake Superior and 4 miles from that of Torch Lake on 

 the east side, the latter being a land-locked arm of the main 

 lake. The rate determined on for this is the average of five 

 different, closely agreeing rates, established between different 

 levels of the mine. The observations made in this and the 

 Tamarack mine were kindly volunteered by Mr. Frank Kle- 

 petko, the mining engineer of the company. 



The Tamarack mine, unfortunately, did not furnish stations 

 that could be regarded as reliable, as they were too close to 

 active mining operations, and my notes show that the effect of 

 the presence of miners, with their lights, blasting and rock- 

 drills (worked by compressed air) give very erroneous results, 

 especially the rock-drills with their ice-cold exhaust. So while 

 I give the results of this mine, they are not to be accepted as 

 satisfactory ; this mine is 4 miles from Lake Superior. 



* "With the " Tamarack " rate omitted, the average thermic gradient is 99* feet 

 to the degree. 



