304 



NATURE 



{Jan. 30, 1879 



chiefly in the " Neues Jahrbuch fiir Mineralogie," &c., and the 

 best authorities seem to be unanimous in rejecting the hypothesis 

 of a retarded rate of increase in the earth's surface as unwar- 

 ranted, either by the Sperenberg observations or any others. 

 Herr Dunker himself concurs in this opinion. Dr. Stapff also, 

 though some of his own empirical formula; indicate a retarded 

 rate of increase, writes to Prof. Everett in the following terms : — 

 "As to my formulas, I beg you to remember that they are not 

 constructed for expressing laws of Nature. They simply are 

 made for facilitating the view over a heap of figures and data of 

 observation. And generally I beg you to be sure that those 

 formulas, in my mind, cannot express any law for the increase 

 of warmth at greater depths than those in which the tunnel 

 observations were made. The formulas give good means for 

 eliminating empirically some of the influences of the shape of 

 surface which occur in the profile of the mountain. " 



Mr. W. Galloway, one of H.M. Inspectors of Mine?, has 

 taken observations in Fowler's Colliery, Pontypridd, South 

 Wales, The shaft is 846 feet deep, and the air current down it 

 amounts to between 20,000 and 30,000 cubic feet per minute. 



In order to determine the normal temperature of the coal, a 

 hole 1 2 inch in diameter was bored in the side of a narrow place 

 that was being rapidly driven in the solid coal. The hole was 

 bored in the very face, to the depth of 4 feet. The thermo- 

 meter (one of the committee's slow-action non-registering instru- 

 ments) was placed at the inner end ; then a wooden cylinder of 

 nearly the same diameter as the bore -hole, and 9 inches long, 

 was pushed in until it came in contact with the copper case of 

 the thermometer ; and lastly a wooden plug, wrapped round 

 with cloth, was diiven firmly into the mouth of the hole. The 

 thermometer was at 58° F. when it was put into the hole, and 

 after remaining there from 2 P.M. on August 25, 1876, to 3.45 

 P.M. on the following day, it stood at 62°* 7, There was no 

 water whatever in the hole, and the depth below the surface of 

 the ground was 855 feet. 



The circumstances of this observation seem to preclude any 

 considerable disturbance of the normal temperature ; and com- 

 bining it with the mean annual temperature at the surface, which 

 is said to be 5i°"5, we have an increase of ii°'2 F. in 855 feet ; 

 which is at the rate of 1° F. for 76 feet. 



Two other observations were taken in other parts of the mine. 

 They are not directly available for the purposes of the Com- 

 mittee, but were intended to test the influence of air-currents on 

 the temperature of the coal ; and they show variations of 2° or 

 3°, according to the season of the year. 



Observations are being taken for the Committee by Mr, G. F, 

 Deacon, Borough Engineer of Liverpool, in a bore which has 

 attained the depth of 1,004 f^^^ i"^ connection with the 

 Liverpool Waterworks at Bootle. 



The temperature at this depth is 58°* I. The observation 

 nearest the surface was at the depth of 226 feet, the temperature 

 at this depth being 52°. We have here a difference of 6''*i, in 

 778 feet, which is at the rate of 1° for 128 feet, and the same 

 rate is approximately maintained throughout the descent. For 

 instance, at 750 feet, the temperature was 56°, which gives 1° 

 for 131 feet by comparison with the depth of 226 feet, and 1° 

 for 121 feet by comparison with the bottom. 



The bore is 24 inches in diameter, and the observations were 

 taken with a protected Phillips's maximum thermometer every 

 Monday morning. The operation of boring was continued up 

 to twelve o'clock on Saturday night, and was not resumed till 

 the temperature had been taken on the following Monday, The 

 time that the thermometer remained at the bottom was not less 

 than a quarter of an hour, and ^^■as sometimes half an hour. 



The rock-formation consists of the pebble beds of the Bunter 

 or lower trias, and most of it is described as hard, close-grained, 

 and compact. The speed of boring is indicated by the dates of 

 the obser\'ations at 226 and 1,004 feet, the former being 

 November 12, 1S77, and the latter August 12, 1878, A month 

 was lost by the jamming of the drilling tool, in May and June, 

 1878, when a depth of about 890 feet had been attained. 



The depth from the surface of the ground to the'surface of the 

 water in the bore has gradually decreased from 66 feet, when 

 the bore was at 318 feet, to 52 feet, when the bore was at 800 

 feet, and to 5ri feet, at the present depth. It would thus 

 appear that the inflow of water from below has increased with 

 the depth attained. There is a slow percolation from the upper 

 part of the water-column to an underground reservoir near at 

 hand, the top of the water-column being considerably higher 

 than the top of the water in the reservoir. Mr. Deacon remarks 



that the slow upward flow v^hich supplies the water for this 

 gradual discharge is favourable to the accuracy of the observa- 

 tions (which have always been taken at the bottom), liy checking 

 the tendency of the colder and heavier upper water to descena 

 and mix with the lower. As bearing on the subject of the dis- 

 turbance of temperature by the stirring of the water in boring, 

 as well as by the generation of heat in the concussions of the 

 tool, it may be mentioned that the last observation before the 

 month's interruption by the jamming of the tool was 57°'5> ^* 

 886 feet, and the first observation after the extraction of the tool 

 was 57°'o, at 898 '6 feet, the former being on May 20, and the 

 latter on July i. The smallness of the difference bet\N een these 

 two temperatures seems to indicate smallness of disturbance by 

 the action of the tool. 



It appears from these various circumstances that the observa- 

 tions are entitled to considerable weight, and that the rate of 

 increase of temperature downwards at Liverpool is exceptionally 

 slow. It will be remembered that the rate found by Mr. Fair- 

 bairn, at Dukinfield Colliery, in the adjacent county (Cheshire), 

 was also very slow, though not nearly so slow as that indicated 

 by these Liverpool observations. — (See our Report in the 

 volume for 1870), 



Mr. E, Wethered, of Weston, near Bath, has also commenced 

 observations in a colliery in that neighbourhood, Mr, J Merri- 

 vale, of Nedderton, near Morpeth, has received a thermometer 

 for observations in a colliery. Mr. J. T. Boot, of Huck- 

 nall, near Mansfield, has received a second thermometer (in 

 place of a broken one) for observations in a deep bore, and 

 Mr, Rowland Gascoigne, of the same town, has received one for a| 

 a similar purpose, I 



In the eleven years which have elapsed since the appointment ™ 

 of this Committee a large amount of useful work has been done, 

 by methods of observation not requiring any elaborate or 

 expensive appliances, or any special training on the part of the 

 observers. 



Two difficulties are encountered in investigating underground 

 temperature. We have to contrive instruments which shall 

 truly indicate the temperature at the point of observation, and 

 we have further to insure that this temperature shall be the same 

 at the time of observation as it was before the locality was arti- 

 ficially disturbed. 



As regards the first of these difficulties the Committee have 

 been completely successful, and have largely increased the 

 resources at the command of observers. 



But in regard to the second difficulty the same amount of 

 success has not been attained. The circulation of water in bore- 

 holes and of air in mines are distvirbing elements difficult to deal 

 with. Even such firm plugging as was employed to isolate por- 

 tions of the water-column in the great bore at Sperenberg cannot 

 altogether remove the error arising from convective disturbance ; 

 for the long-continued presence of water at a temperature dif- 

 ferent from that proper to the depth affects the temperature of 

 the surrounding rocks, and the temporaiy isolation of a short 

 column would not abolish this source of error, even if the plugs 

 themselves were impervious to conduction and convection. 



After the experience which has now been gained of rough and 

 ready methods, it is time to consider the propriety of resorting 

 to a more special method, which has been more than once 

 suggested, but has hitherto teen postponed on account of the 

 additional labour and skill which would be requisite for carrying 

 it out. 



There can be no doubt that the surest way to bring any point 

 of a boring to its original temperature is to fill up the bore, and 

 reduce it as nearly as possible to its original condition. Several 

 instruments have been contrived which, when buried in the 

 earth, with wires coming from them to the surface, admit of 

 having their temperature observed by electrical means. 



One of these is Siemens' resistance thermometer, another is 

 Wheatstone's telegraphic thermometer, of which a description 

 will be found in the Report of the Dundee Meeting of the 

 British Association ; another is Becquerel's thermo-electric appa- 

 ratus, which has been employed by its inventor and his son and 

 grandson for some forty years. It is described in the following 

 terms in the first Report of this Committee (1868) : — 



" The thermo-electric method might also be followed with ^_ 

 great advantage. Two wires, one of iron and the other of ^H 

 copper, insulated by gutta-percha or some other covering, as in ^V 

 submarine cables, and connected at their ends, might be let 

 down so as to bring their lower junction to the point where the 

 temperature is to be taken, their upper junction being immersed 



