22 REMARKS ON TEMPERATURE OF THE EARTH IX MINES. 



level ; at 530 feet, thermometer 70 degs. ; and at 560 feet, 70 

 degs. ; and in the face of cross cut, where a man was at work, 

 350 feet from the shaft, with no opening or division, thermo- 

 meter 77 degs, and at 678 feet down the shaft, thermometer 71 

 degs., with no artificial ventilation, but holed into the 560 ft. level. 

 Thence to top of shaft, at 3h. 30m. p.m., thermometer 80 degs. 

 It may here be stated that tlie height of all the mines (at the 

 surface) above sea level is from 800 to 150 feet, and that 

 practically they are therefore on the same horizon. The rock, 

 although varying somewhat from slates and grits, through a 

 conglomerate of varying aspect and texture, to a highly crys- 

 talline form, the place of Avhich is scarcely decided, may be taken 

 as offering no strong points of divergence in its conductive pro- 

 perties ; beds of limestone are in the series, but no granite or 

 ■other plutonic or volcanic rocks. 



There are many other mines at Gympie, none of which 

 promise any variety or divergence of results. The metal mined 

 for is gold exclusively, and it is not encumbered to any consider- 

 able extent by the presence of other metals. 



The accompanying influences have in each case been noted 

 in order that the means of forming a conclusion may be at hand. 

 There does not appear to me, however, to be any reason to 

 suppose that at any depth to which we have yet attained, there 

 need necessarily be any increase of temperature beyond the 

 normal heat of the invariable plane which may be a few fathoms 

 below the surface. 



The most noticeable feature of the statistics published on 

 this subject is the great irregularity of the increase, which must 

 go far to prove that the change is not due to any general internal 

 heat of the earth but to local and special circumstances, which 

 have more effect than the supposed internal heat of the earth, 

 which, even if more intense, is further aAvay, and may have a 

 similar relative influence in this direction at any depth to which 

 man has yet penetrated, to that of the sun to the moon in their 

 influence on the tides of the ocean at the surface. 



Mr. Hemwood, F.R.S., F.G.S., &c., above quoted, gives, in 

 the transactions of the Royal Geological Society of Cornwall, 

 certain observations taken in the Colorado mine, Chili. The 



