552 



NATURE 



\OcL 3, 1889 



moved to a measured distance from the fixed one, and the space 

 between them is then filled with clay which has been made 

 plastic by kneading it with water, so that it forms a cylinder with 

 the two disks. 



When the pole presses on the bottom of the bore, part of the 

 weight of the boring rods is supported on the upper disk, thus 

 squeezing the clay against the sides of the bore and forming a 

 water-tight plug. 



The above description applies especially to the taking of ob- 

 servations at the bottom of the bore. When it was desired to 

 isolate a column of water at a considerable distance from the 

 bottom, the apparatus employed consisted of two portions. The 

 above description applies to the upper portion, and the lower 

 portion was similar to it but inverted, resting upon rods which 

 extended to the bottom. The two masses of clay in this case 

 cut off a water-column between them. 



Experiments with a model, in which the bore was represented 

 by a cylindrical glass vessel 26 cm. high and 55 mm. wide, filled 

 with water, showed that the isolation was very good, and that it 

 remained so though the immersion lasted more than ten hours. 

 In tearing away the clay from the vessel a portion of the clay 

 (fell into the water, but such . an accident occurring in the bore 

 would be of no consequence. 



The construction of the isolating apparatus was intrusted to 

 Bore-Inspector Kobrich, under whose management the observa- 

 tions were to be carried out. 



Besides the thermometer in the isolated water-column, there 

 ■was a second maximum thermometer in the open water just 

 above the upper plug, for comparison, the height of its bulb 

 above that of the principal thermometer being 2 "8 m. 



The thermometers were very similar to those employed at 

 Sperenberg. They were overflow-thermometers, generally with- 

 out scales, and^were inclosed (for protection against pressure) in 

 a hermetically sealed' case of stout glass with an external diameter 

 of 15 mm. To take the reading, the thermometer, after being 

 drawn up, was put with a normal thermometer into a vessel of 

 water at a temperature a little below that which was expected. 

 Warm water was then gradually added, and the whole kept 

 stirred till the mercury in the overflow-thermometer reached the 

 open end. The temperature at this moment was then read by 

 the other thermometer. 



The first observations taken were in the untubed portion of 

 the bore, which at that time extended from the depth of 1240 m. 

 to 1376 m. ; and as the bore was deepened to 1748 m. the ob- 

 servations were continued. In this way the last sixteen observa- 

 tions of Table I. were obtained, forming a series at intervals of 

 30 m. from 1266 m. to 1716 m. of depth. 



A pause which subsequently occurred in the sinking of the 

 bore, through having to wait for a new tube, was utilized for 

 taking the observations which form the remainder of the table. 

 We have thus a complete series of observations, at equal intervals 

 of 30 m., from the depth of 6 m. to that of 1716 m. : 8° -3 R. at 

 6 m., and 45°"3 R. at 1716 m. 



The table is arranged in five columns. The first column con- 

 tains the natural numbers from one to fifty-eight, for convenience 

 of reference to the observations at the fifty-eight different depths ; 

 the second column contains the depths in metres ; and the third 

 column, the temperatures observed at these depths in isolated 

 water-columns. The fourth column contains the excess of the 

 temperature so observed above the temperature observed by 

 means of the secondary thermometer in the free water just 

 above the plug. The fifth column contains the differences 

 between the successive numbers in the third column — in other 

 words, the increase of temperature for each 30 m. of depth. 



The smallness of the effect of isolation, as shown in the fourth 

 column of the table, is very noteworthy, its greatest value being 

 1° R., and its average value about \ of 1° R. At Sperenberg it 

 amounted in several cases to about 3° R. The smallnef s of the 

 effect in the present case is attributable to the narrowness of the 

 bore, which tells in two ways : there is more frictional resistance 

 to the movement of the water ; and the thermal capacity of a 

 given length of column is less in comparison with its surface of 

 contact with the sides of the bore. 



As a further experiment on the prevention of convection, a 

 wooden plug was driven into the bore at the depth of 438 m., 

 thick mud was introduced till it filled all the bore above this 

 plug, and observations were taken with a maximum thermometer 

 in the mud at depths from 426 m. to 126 m. A second plug was 

 then driven in at the top of the tubing, which was 120 m. beneath 

 the surface of the ground, and the observations were continued 



upwards from 118 m. to 6 m. The observations thus taken in 

 the mud are given. They are rather higher than those previously 

 obtained at the same depths, the greatest difference occurring at 

 the depth of 276 m., where it amounts to o°'9 R. Herr Dunker 

 suggests that the difference may have arisen from insufficient 

 time being allowed for the mud to take the permanent 

 temperature. 



Upon the whole it is clear that in this great bore the disturb- 

 ing 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 5630 feet, in a new bore where there has not been time 

 for the original heat to be lost by exposure, forms undoubtedly the 

 most valuable contribution ever made to the observation of under- 

 ground temperature. The official to whose initiative the obser- 

 vations are due is Chief-Mining-Captain Huyssen, of Berlin. 

 The expense of sinking the bore was ;^io,ooo sterling, the time 

 required for hauling up the boring rods was ten 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 several times in the part corresponding to the tubed por- 

 tion 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 1266 m. to 17 16 m., lies 

 slightly above its chord ; but the curve from either 6 m. or 36 m, 

 to 1500 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 ob- 

 servation of all, which is at 1716 m., we have an increase of 

 36°-5 R. in 1680 m. This is a difference of 82°"i F. in 5512 

 feet, which is at the rate of 1° F. in 67 'i 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, on the assumption that it passes accurately 

 through the point determined by the observation at 36 m., and 

 he thus obtains a mean rate of increase of 0*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 

 Westinghouse, Jun., of Pittsburg, President of the Philadelphia 

 Company, with the view of obtaining observations of tempera- 

 ture from some of the deep oil and gas wells belonging to the 

 Company. Mr. Westinghouse has purchased three of the Com- 

 mittee's maximum thermometers, and has intrusted the taking of 

 the observations to Mr. A. Cummins, the Company's Mining En- 

 gineer and Geologist. Some attempts have been made at 

 observation, 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 Pittsburg, known as the Dilworth well, where the 

 following results were obtained : — 



The well was sunk to a depth of 4625 feet, but no observations 

 were made except at the depths specified. The thermometer 

 remained only from five to ten minutes during each test ; and as 

 there were only 40 feet of water in the well, the observations 



