28 BEPORT— 1880. 



general result is in harmony with what has been found at the nearest 

 localities mentioned in our previous reports, namely, Dukinfield and Liver- 

 pool. Here, as at Dukinfield, all the strata are highly inclined. 



Some additional observations at Dukinfield have recently been made 

 for the Committee, by Mr. Edward Garside, student of engineering in 

 Queen's College, Belfast. The Astley Pit, in which they were taken, has 

 now been carried to a much greater depth than it had extended at the 

 time of Sir Wm. Fairbairn's observations, to which allusion was made in 

 our Report for 1870. The two deepest seams of coal in it are called the 

 ' Cannel Mine ' and the ' Black Mine,' the former being the deeper of 

 the two ; they both slope downwards at about 15°, the deepest point being 

 the far end of the Cannel Mine. The following is Mr. Garside's summary 

 of the observations ; the ' surface-depth ' being distinguished fi-om the 

 ' shaft-depth ' because the surface is not level, but slopes slightly in the 

 same general direction as the seams. The shaft-depth gives the difference 

 of levels, but the surface-depth, which is practically the same as the 

 distance of the nearest point of the surface, is what we must use in com- 

 puting the rate of increase of temperature. 



The pit is described as being entirely free from water. 



All the observations were taken with one of the Committee's slow- 

 acting thermometers, in holes drilled in the floors at ihe far ends of newly 

 opened horse-road levels ; the holes being 4 feet deep and 2 inches in 

 diameter. All the holes were free from cracks, and were in the same kind 

 of rock — an argillaceous earth called ' warren earth.' They were allowed 

 to stand for a short time, to allow the heat caused by drilling to escape. 

 The thermometer was then inserted, and the portion of the hole between 

 it and the mouth plugged with cotton waste and the dust which came 

 out of the hole in drilling. After being left for forty-eight hours, it 

 was taken out and read. 



Arranging the observations in the order of the surface-depths, we have 

 the following data : — 



-■o 



Senm Surface Temiieratiirp Feet per Degree 



^°"™ Depth lemperature from Surface 



Black .... 1,987* >. .74 . . 79-5 



, 2,407| . . 80 . . 77-7 



Cannel .... 2,416i . . 81 . . 75-5 



„ .... 2,700 . . 86| . . 72 



The numbers in the last column are calculated from an assumed 

 surface-temperature of 49°, and show that the increase of temperature 

 becomes more rapid as the depth increases. If, without making any 

 assumption as to surface-temperature, we compare the observations among 

 themselves, the two shallower give an increase of 6° in 420 feet, which is 

 at the rate of 1° in 70 feet, and the two deeper give an increase of 5^° in 

 283^ feet, which is at the rate of 1° in 51-| feet, a result which confirms 

 the increase of rapidity with depth. 



The greatest depth in Sir Wm. Fairbairn's observations was 685 yards 



