ON UNDERGROUND TEMPERATURE. 33 



downwards in this direction, may exercise an important influence in assimi- 

 lating the temperature at great depths to that which prevails near the surface. 

 Mr. Hull's own statement of his views is given in the footnote below*. 



Mr. M'Farlane has been prevented from continuing his observations near 

 Glasgow during the past year by the press of business incident to the removal 

 from the old to the new College. 



Mr. F. Amery, Druid House, Asliburton, Devon, has taken some observa- 

 tions with one of the Committee's thermometers in the shaft of a mine which 

 had been unused for a year and was nearly full of water. The shaft is 12 feet 

 X 7 feet, and descends vertically for 350 feet, after which it slopes to the 

 south at an angle of 50°, continuing to the depth of 620 feet. The water stood 

 at 50 feet from the surface. Mr. Amery observed the temperature at every 

 50th foot of depth in the vertical portion, and found it to be 53° at all depths, 

 except at 250 feet and 200 feet, where it was 53-4 and 53*2 respectively. A 

 copper lode crosses the shaft at the depth of 250 feet ; and it appears to be 

 generally the case, in the Cornwall and Devonshire mines, that copper lodes 

 exhibit high temperature — a circumstance which Prof. Phillips explains by 

 the conformation of the strata, which is such as to cause water from greater 

 depths to make its way obliquely ujjwards by following the course of the 

 copper lodes. 



The nearly constant temperature observed from the surface to the bottom 

 of the shaft seems to indicate a large amount of convective circulation. In 

 this respect small bores have a decided advantage. 



Mr. Gr. A. Lebour has taken observations with our thermometers in seve- 

 ral shafts and bores near Eidsdale, Northumberland, made for working coal 

 and ironstone. Mr. Lebour does not report the temperatures observed, which 

 he characterizes as discrepant and utterly valueless, owing, he believes, to the 

 numerous water-bearing beds which they cut through, and the very varying 

 temperature of these waters. Having now, however, found a dry bore, he 

 hopes to make a useful series of observations next winter. 



One of the Committee's thermometers has recently been sent to Mr. John 

 Donaldson, C.E., Calcutta, who has expressed his desire to aid in scientific 

 observation, and, being now engaged in examining for coal and iron under 

 Government, is likely to render us effective service. 



Shortly after the last Meeting of the Association, the Secretary of this Com- 



* " Rose-Bridge Colliery oceupies a position in the centre of a gently sloping trough, 

 where the beds are nearly horizontal ; they are terminated both on the west and east by 

 large parallel faults which throw up the strata on either side. The Colliery is placed in 

 what is known as ' the deep belt.' 



" Dukenfield Colliery, on the other hand, is planted upon strata which are highly in- 

 clined. The beds of sandstone, shale, and coal rise and crop out to the eastward at 

 angles varying from 30^ to 33°. Now I think we may assume that strata consisting of 

 sandstones, shales, clays, and coal alternating with each other are capable of conducting 

 heat more rapidly along the planes of bedding tlian across them, different kinds of rock 

 having, as Mr. Hopkins's experiments show, different eonducting-powers. If this be so, 

 we have an evident reason for the dissimilar results in the two cases before us. Assuming 

 a constant supply of heat from the interior of the earth, it could only escape, in the case of 

 Rose Bridge, across the planes of bedding, meeting in its progress upwards the resistance 

 offered by strata of, in each case, varying eonducting-powers. On the other hand, in the 

 case of Dukenfield, the internal heat could travel along the steeply inclined strata them- 

 selves, and ultimately escape along the outcrop of the beds. 



" I merely offer this as a suggestion explanatory of the results before us, and may be 

 allowed to add tliat the strata at Monkwearmouth Colliery, the thermometrical observa- 

 tions at which correspond so closely with those obtained at Rose Bridge, are also in a 

 position not much removed from the horizontal, which is some evidence in corroboration 

 of the views here oflPered." — Proc. Boy. Soc. 1870, vol. xviii. p. 175. 



1870. jD 



