96 REPORT—1885. 
Comparing consecutive depths from 546 feet downwards, we have the 
following increments of temperature :— 
34° in 234 ft., giving 1° for 67 ft. 
34° ,, 240 ,, ” 69 ,, 
210 ~ 7. 
35 ” 252) »55 ” 72 55 
—showing a remarkably regular rate of increase. A comparison of the 
first and fourth observations gives an increase of 105° in 726 feet, which 
is at the rate of 1° F. in 69°1 feet. As the surface slopes about 1 in 5, and 
the pit is near the summit of a ridge, it is probable that in level ground 
of similar material the rate would be about 1° F. in 60 feet. 
As a check upon this result, we find that this rate of decrease reck- 
oned upwards from the smallest depth (546 feet) would give a surface 
temperature of (56 — 7-9 =) 48°'1, which, as the elevation is 800 feet, is 
probably very near the truth. 
Mr. Garside has sent an observation of temperature taken by himself 
in the roof of the Mersey tunnel in August 1883. The temperature was 
53°, the depth below Ordnance datum being 92 feet. A great quantity 
of water from the river was percolating through the sides of the tunnel. 
On August 13, 1884, he verified his previous observation in Denton 
Colliery (15th Report). The second observation was made at the same 
depth as the first (1,317 feet), in the same pit and level, and under the 
same circumstances, except that the thermometer was allowed to remain 
fourteen days in the hole bored for it, instead of only six hours. The 
temperature observed was the same as before, namely 66°. 
Mr. Garside has also supplemented his previous contribution to our 
knowledge of the surface temperature of the ground in the Hast Man- 
chester coal-field (16th Report) by two more years’ results from the 
same observing stations. The following are the collected results, includ. 
ing the year previously given :— 
Croft House, in the centre of Ashton-wnder-Lyne, 345 ft. above sea. 
| Mean of Max. 
= 4 ft. Deep 1 ft. Deep | ‘and Min. Air 
1gs2 | 4795 4452-2 48°-4 
1883 | 46°6 45°°5 47°-8 
1884 |  48°3 47°°3 48°-9 
Means | 47-5 46°°3 48-4 
District Infirmary, 501 ft. above sea. 
Mean of Max. 
— | 4 ft. Deep 1 ft. Deep and Min. Air 
1882 45°-9 45°°6 46°°6 
1883 46°°3 45°°3 46°°3 
1884 AT°-7 47°3 48°-2 
Means | 46°°6 46° 1 47°-0 
ee EE 
Giving equal weight to the 4-foot and 1-foot ‘observations, we have @ 
mean surface temperature of 46°-9 at an elevation of 345 feet, and 46°°4 
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