ON THE BATE OF INCREASE OF UNDERGROUND TEMPERATURE. 39 



Upon tlio whole it is clear that in this great bore the disturbing effect 

 of convection is very small, and that, such as it is, it has been almost 

 annihilated by the very efficient system of plugging adopted. The series 

 of observations now before us, extending as it does by regular stages 

 from the surface to a depth of 5,G30 feet, in a new bore where there has 

 not been time for the original heat to be lost by exposure, forms un- 

 doubtedly the most valuable contribution ever made to the observation of 

 ■underground temperature. The official to whose initiative the observa- 

 tions are due is Chief-Mining-Captain Hnyssen of Berlin. The expense 

 of sinking the bore was 10,000Z. sterling, the time required for hauling 

 up the boring rods was 10 hours, and their united weight was 20 

 tons. 



On plotting the temperatures so as to exhibit temperature as a 

 function of depth, the curve obtained approximates very closely to a 

 straight line. A straight line joining its two ends meets the curve 

 Boveral times in the part corresponding to the tubed portion of the bore, 

 which is about three fourths of the whole ; while in the remaining fourth, 

 (forming the deepest portion of the bore) all the temperatures except 

 the first and last lie above the straight line. In this statement it is to 

 be understood that depth is represented by distance laid off horizontally, 

 and temperature by distance laid off vertically upwards. 



The question whether the curve on the whole bends upwards or 

 downwards is of some interest, because it is equivalent to the question 

 whether the rate of increase is accelerated or retarded as we go deeper. 

 The evidence on this point is undecisive. The curve for the untubed 

 portion, from 1,266 m. to 1,716 m., lies slightly above its chord; but the 

 curve from either 6 m. or 36 m. to 1,500 m. lies for the most part below 

 its chord. 



Taking the observation at 36 m. as the first which is free from 

 atmospheric disturbance, and comparing it with the deepest observation 

 of all, which is at 1,716 m., we have an increase of 36"5° Reaumur in 

 1,680 m. This is a difference of 82-1° Fahrenheit in 5,512 feet, which 

 is at the rate of 1° F. in 67-1 feet. 



Herr Dunker, after an elaborate discussion of the question whether 

 the curve on the whole bends upwards or downwards, arrives at the 

 conclusion that it is best represented by a straight line. He applies the 

 method of least squares to find the slope of this straight line, and 

 thus obtains a mean rate of increase of '0224276 of a degree Reaumur 

 per metre, which is equivalent to 1° F. for 65'0 feet. 



The Secretary has been in correspondence with Mr. George Westing- 

 house, junr., of Pittsburgh, President of the Philadelphia Company, with 

 the view of obtaining observations of temperature from some of the deep 

 oil and gas wells belonging to the Company. Mr. Westinghouse has 

 purchased three of the Committee's maximum thermometers, and has 

 entrusted the taking of the observations to Mr, A. Cummins, the Com- 

 pany's Mining Engineer and Geologist. Some attempts have been made 

 at ob.servation, but owing to press of business they have not been 

 thoroughly carried out. Mr. Cummins states that ' there has been a 

 constant strain to bring up the supply of gas to the requirement of the 

 city's needs, and every hour of delay is watched very jealously.' 



The most successful attempt was made in a well at Homewood in the 

 city of Pittsburgh, known as the Dilworth well, where the following 

 results were obtainnd • — 



