66 REPORT — 1901. 



various parts of Michigan. It includes temperatures of deep wells 

 spouting above ground and of shallow springs. Mr. Lane's general result 

 is that — 



' in the flat, undisturbed sedimentaries of the Lower Peninsula [between 

 Lake Michigan and the lower lakes] the geothermal gradient is not far 

 from 1° in 67 feet ; while in the Upper Peninsula, near Lake Superior, 

 tlie gradient is perhaps a little lower than 1° in 100 feet. This difference 

 may be ascribed to the difierence in conductivity, to which the geothermal 

 gradient should be inversely proportional. The Upper Peninsula rocks 

 are probably more conductive (trap -007) when dry, and certainly are 

 less porous and contain less water than those of the Lower Peninsula 

 (limestone "005, sandstone '002. There has been no volcanic or very 

 extensive orogenic disturbance since early Cambrian times, and but little 

 Palseozoic faulting and folding. You will notice that the temperatures 

 of shallow flows are higher than the mean annual temperatures as derived 

 from the Weather Service ; which is not surprising when we consider 

 that in the winter the surface of the ground is often blanketed with snow 

 and not freezing, when the air temperatures are very low.' 



Mr. Lane estimates the ' mean annual temperature ' for the Calumet 

 district at 38°"6, and the ' mean temperature at the depth of no variation ' 

 at 40°. If we take this latter as the temperature at 50 feet, and compare 

 it with the temperature 84° at 4,450 feet in the Tamarack mine, we have 

 an increase of 44° F. in 4,400 feet, or 1° in 100 feet. Mr. Lane's 

 estimate for the Calumet district is 1° F. in 107 feet. He states that 

 numerous corroborative data indicate a gradient lying between 1° in 

 lOOfeet and l-- in 115 feet. 



No authorities are cited for the conductivities which Mr. Lane assigns 

 to the rocks, and fuller information on this point is desirable ; but, in 

 view of the fact that the President of Section C last year characterised 

 the variation in the British Isles ' from 1° in 34 feet to 1° in 92 feet' as 

 ' a surprising divergence of extremes from the mean,' it is well to 

 emphasise the connection between gradient and conductivity. If there is 

 anything like uniformity in the annual escape of he<at from the earth at 

 different places, there must necessarily be large differences in geothermic 

 gradients, since the rate of escape is jointly proportional to the gradient 

 and the conductivity. 



The investigation of underground temperature is being energetically 

 taken up by the United States Geological Survey. Mr. N. H. Darton 

 has for some years been engaged in collecting data with a view to the 

 preparation of an isogeothermal map of the United States. 



Brief allusions have appeared to observations taken in 1893 in a bore 

 at Paruschowitz, near Rybnik, in Upper Silesia, reputed to be the deepest 

 in the world. The details, strange to say, have never yet been published, 

 but they have been kindly furnished for the purposes of this report by 

 the Prussian mining authorities. 



The bore is one out of a large number (400 or more) which have been 

 sunk by the Prussian Government for the purpose of exploring the mineral 

 resources of the country. A full account of the mode of sinking it and 

 the difliculties which were encountered was given by Bergrath Kobrich 

 at the ninth ' Wanderversammlung ' of boring engineers, and is printed 

 in the mining journal ' Gliickauf ' for 1895, pp. 1273-1277. 



The boring was begun in January 1892, and finally discontinued in 



