BY WJI. FRYAR, INSPECTOR OF JUNES, QUEENSLAND. 20 



given, and show a ratio as high as 1 cleg, for each 30 feet, while 

 the majority show 1 deg. for 40 to 50 feet. He further says 

 that the general result of a complete discussion of these 

 observations on subterranean temperature made in mines 

 and collieries appear to give a ratio of 1 deg. centigrade in 25 

 metres, or 1 deg. Fahr. for 45 English feet. Kupffer, after an 

 extensive comparison of the results in different countries, makes 

 the increase 1 deg. for about 37 English feet. Cordier is of 

 opinion that the increase would not be overstated at 1 deg. for 

 45 feet, but he says the increase does not follow the same law being 

 twice or thrice as much in one country as another, Anstead 

 says : — " The increase of temperature in deep mines appears to 

 vary according to some law which is not at present understood." 

 Sir C. Lyall says in Saxony it was necessary to descend thrice 

 as far in some mines as in others for each additional degree of 

 temperature. 



Some geologists calculate that the solid crust of the earth 

 is only ten miles in thickness. Hopkins says it cannot be 

 less than one-fifth or one-fourth of the earth's radius, i.e., 800 

 or 1,000 miles as a minimum, but it may be anything higher. 



Professor Hull, in a paper read before the Geological Society 

 of Edinburgh during the present year, appears to think that 

 notwithstanding a probable increase of output, the coal of Great 

 Britain will last 1,000 years. He points out that coal is now being 

 worked to a depth of 3,000 feet in Lancashire and Cheshire, 

 and he believes that by the end of the century such depths will 

 not be at all unusual, and he evidently implies that very much 

 greater depths will be reached, as there is certainly not sufficient 

 coal within that depth to yield the supply he anticipates. 



A shaft 2,000 feet deep is less than one-ten-thousandth 

 part of the earth's radius, but most of the observations on 

 which the theory is based were taken at depths of only a few 

 hundreds of feet, the average of which may have been one-fifty- 

 thousandth part of the radius, a portion so exceedingly slight 

 that it is quite impossible to found any theory upon it, even if 

 the observations all pointed in one direction, but when we see 

 that in nearly every case the results point to local peculiarities 

 and are at variance with each other, we cannot avoid the con- 



