FRAGMENTS OF SCIENCE. 



281 



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Some New Observations on Underground 

 Temperatures. Some recent observations on 

 underground temperatures are described in 

 the December number of the American Jour- 

 nal of Science by Prof. A. Agassiz. He 

 says : " For several years past I have, with 

 the assistance of Mr. Preston C. F. West, 

 been making rock temperature observations 

 as we increased the depth at which the min- 

 ing operations of the Calumet and Hecla Min- 

 ing Company were carried on. We have 

 now attained at our deepest point a vertical 

 depth of 4,712 feet, and have taken tem- 

 peratures of the rock at 105 feet; at the 

 depth of the level of Lake Superior, 655 

 feet; at that of the level of the sea, 1,257 

 feet; at that of the deepest part of Lake 

 Superior, 1,663 feet ; and at four additional 

 stations, each respectively 650, 550, 561, and 

 1,256 feet below the preceding one, the 

 deepest point at which temperatures have 

 been taken being 4,580 feet. We propose 

 when we have reached our final depth, 4,900 

 feet, to take an additional rock temperature, 

 and to then publish in full the details of our 

 observations. In the meantime it may be 

 interesting to give the results as they stand. 

 The highest rock temperature obtained at the 

 depth of 4,580 feet was 79 F. ; the rock tem- 

 perature at the depth of 105 feet was 59 F. 

 Taking that as the depth unaffected by local 

 temperature variations, we have a column of 

 4,475 feet of rock with a difference of tem- 

 perature of 20 F., or an average increase of 

 1 F. for 223-7 feet. This is very different 

 from any recorded observations, Lord Kel- 

 vin, if I am not mistaken, giving as the in- 

 crease for 1 F., fifty-one feet, while the ob- 

 servations based on the temperature obser- 

 vations of the St. Gothard Tunnel gave an 

 increase of 1 F. for sixty feet. The calcu- 

 lations based upon the latter observations 

 gave an approximate thickness of the crust 

 of the earth in one case of about twenty 

 miles, in the other twenty-six. Taking our 

 observations, the crust would be over eighty 

 miles, and the thickness of the crust at the 

 critical temperature of water would be over 

 thirty-one miles, instead of about seven and 



8*5 miles as by the other and older ratios. 

 . . . The holes in which we placed slow 

 registering Negretti and Zambra thermom- 

 eters were drilled, slightly inclined upward, 

 to a depth of ten feet from the face of the 

 rock and plugged with wood and clay. In 

 these holes the thermometers were left from 

 one to three months. The average annual 

 temperature of the air is 48 F. ; the tem- 

 perature of the air at the bottom of the 

 shaft was 72 F." A possible source of er- 

 ror in these observations arises from the free 

 access which the surface air has to the 

 mine, and the probable effect which it 

 must exercise on the rock temperature for 

 many feet about it. This is, of course, also 

 true of the previous observations, conducted 

 in mines or tunnels. Another feature which 

 would perhaps introduce a source of error 

 is the close proximity of the enormous mass 

 of water in Lake Superior. It seems prob- 

 able that the rock temperature in this whole 

 region is largely modified by the vast body 

 of water in the lake system. 



The Northern Appalachians. A con- 

 cise, satisfactory summary of the character- 

 istics of the northern Appalachian Mountain 

 ranges is given by Mr. Bailey Willis in a pa- 

 per published in the series of Monographs 

 of the National Geographic Society. In- 

 stead of being marked by a central crest, as 

 is usually the case, these ranges are charac- 

 terized by a central zone, the surface of 

 which is lower than the ranges on either 

 side. This zone is a very complex valley, 

 or series of valleys, and is known by dif- 

 ferent names in different sections of its 

 length of a thousand miles. Two principal 

 ranges bound it one on the southeast, gen- 

 erally known as the Blue Ridge, and the 

 other on the northwest, known as the Alle- 

 ghany Front. They extend in two nearly 

 parallel lines about seventy-five miles apart, 

 and have each its special characteristics. 

 The rivers flow either to the Atlantic or to 

 the Ohio River. The divide between these 

 groups of streams is winding and often incon- 

 spicuous, and has no definite relation to the 



