ON THE EATE OF INCREASE OF UNDERGROUND TEMPERATURE. 73 



shales which are 8 feet in thickness, forming the floor of the ten yards 

 coal and roof of the Heythen coal, the total thickness of the seam worked 

 (with small parting) being about 52 feet. The temperature observed 

 was 57°-5 F. which, with an assumed surface temperature of 49°, gives 

 an increase of 8°-5 in 700 feet, being at the rate of 1° F. in 82 feet. 



The colliery is situated on the summit of a hill 822 feet above sea- 

 level, so that the point at which the observation was taken was 122 feet 

 above sea-level. The convexity of the ground must be taken into account 

 as one element in endeavouring to account for the slowness of the ob- 

 served rate of increase. Of the 700 feet of superincumbent shales, about 

 470 consist of coal measures, 165 of clay marl, and 65 of basalt, connected 

 with dykes whose many branches traverse the coal at slopes varying from 

 vertical to horizontal. The basalt is found to contain, when newly cut 

 open, a remarkable quantity of salt water ; and the charred coal next to 

 the dyke is as porous as ordinary coal cinders for a distance of several inches 

 from the dyke. 



The Secretary has had a correspondence with Mr. Garside respecting 

 the quantity of water found in the East Manchester coal-field. This 

 quantity is very large, as appears from a list furnished by Mr. Garside of 

 the number of gallons pumped per minute from each of thirteen pits 

 during the sinking, the list being given on the authority of William 

 Seddon, Esq., mining engineer, who was contractor for the sinking of 

 them. The average is 360 gallons per minute for each pit, the highest 

 being Denton Colliery with 1,000 gallons, and the lowest Valley Pit, 

 Denton, with 120 gallons. Particulars are also given of the quantity 

 now pumped from some of the collieries, amounting in some cases to 800 or 

 900 gallons per minute. Some of the collieries have been repeatedly 

 flooded, and one is mentioned (Lord's Field Colliery) which was aban- 

 doned on account of water, though its owners were makers of hydraulic 

 machinery, and tried their utmost to keep the water down. Some of the 

 pits were formerly the sources of water-supply for towns in the district. 

 In Astley Deep Pit, Dukinfield, the shaft is ' tubbed ' with cast-iron rings 

 to keep the water back ; and most of the shafts in the district are made 

 as water-tight as possible. Mr. Garside refers to the ' Memoir of the 

 Geological Survey round Oldham,' as stating, on page 45, that five million 

 gallons a day are estimated as being raised from the New Red Sandstone. 



The question naturally arises whether this abundance of water does 

 not exert a powerful cdnvective action, and furnish the explanation of the 

 slow increase of temperature downwards, which has been observed not 

 only in the coal mines of this district but also in a still more marked 

 degree at the Liverpool waterworks at Bootle. 



Nine years having elapsed since the last observations were furnished 

 from the great well at La Chapelle in the north of Paris, which was then 

 in course of sinking, the Secretary has put himself in communication with 

 the contractors to learn what progress has been made, and has received a 

 letter dated July 8, 1882, giving a history of the undertaking during the 

 interval. 



The continual crumbling down of the sides rendered tubing necessary, 

 and a tube was accordingly constructed 677m. long, l-3m. in diameter, 

 and 2 centimetres thick. During the lowering of it, a portion 120m. 

 long broke ofi" and fell to the bottom, leaving another piece 100m. long 

 suspended. This suspended piece was successfully extracted without 

 difficulty, but the fallen piece was not easily dealt with. It was first cut 



