TRANSACTIONS OF THE SECTIONS. 



55 



231 and 685 yards, we have an increase of temperature from 57|° to 75^°, or 17|° 

 Fahrenheit. That is a mean increase of P in 76'8 feet. This rate of increase is not 

 widely different from that observed by other authorities. Walferdin and Ai-ago 

 found an increase of P in 59 feet in the artesian well at Grenelle. At the salt- 

 works at Rehme, where an artesian well penetrates to a depth of 760 yards, or 

 rather more than the Dukinfield mine, the increase is P in 54'7 feet. MM. De la 

 Rive and Marcet found an increase of 1° in 51 feet at Geneva. Other experiment? 

 have given an increase of P in 71 feet. In one respect the observations in the 

 Dukintield mine are peculiarly interesting, as they give the temperature in various 

 descriptions of rock, which appear to prove what has hitherto oeen partially sus- 

 pected, that the conducting powers of the rocks exercise a considerable intluenca 

 on the temperature of the steata. If we add to this the influence of the percolation 

 of water, we shall probably have a sufficient explanation of the m-egid.arities observed 

 in the experiments. 



In Plate I. I have attempted to show graphically the results obtained between' 

 the depths of 231 and 717 yards. The dots show the actual experimental relation 

 of depth and temperature, arranged on a Table in which the ordinates are depths 

 and the abscissfe temperatures. Between these I have dravra a line of variable cur- 

 vature, which expresses approximately the rate of increase in descending through 

 the strata. Between the extreme indications which are most reliable I have drawn 

 a straight line which expresses the theoretical rate, or a uniform increase of P in 

 76'8 feet of vertical descent. Beside the Table of curves is placed a section of the 

 strata of the mine. 



Since the above was wi-itten I have received from Dukinfield some further expe- 

 riments obtained in the same manner in a new shaft which is being sunk at no 

 great distance from the former. The following Table gives the results of these 

 experiments : — 



Table II. — Obser\'ations of the Increase of Temperature in the Dukinfield 



No. 2 Pit. 



Strata. 



Blue shale. 

 Blue shale. 

 Blue shale. 



Blue shale 



Strong grey shale ... 

 Strong grey shale..., 

 Strong grey shale .. 

 Huncliffe red rock . . . 

 Hunoliffe red rock... 

 HuncUtfe red rock ... 



Grey shale 



Grey shale under 



Lane Mine 



Grey shale under 



Lane Mine 



Bituminous shale .... 



Bituminous shale . 

 Bituminous shale . 

 Grey rock 



Remarlu. 



In this Table the thermometer 

 was always placed in a dry 

 sump hole, except on April 

 12, 1860, when the hole was 

 wet. Up to April 30, 1859, 

 five men were at work in the 

 pit at the time of making the 

 observations, and after that 

 time six men. 



This Table shows an increase of temperature of P Fahrenheit for every 106 feet 

 descent. 



From the above and similar obsei-vations we have evidence of the existence in 

 the earth of internal heat, the temperature, so far as can be ascertained, increasing 

 in the simple ratio of the depth. I do not, however, presume to offer an opinion 



