42 kepoet — 1879. 



of the three divisions of the Bristol coal-field, and their dip, where not 

 faulted or disturbed, is about one in six. 



The depths of the places of observation were determined by Mr. 

 Munro, teacher of mining and surveying in the Bristol Mining School, 

 and the surface-temperature is assumed to be identical with the mean 

 temperature of the air for the last fifteen years at Clifton (3 miles distant), 

 according to the observations of Dr. Burden, which is 48*7. The surface 

 of the ground at the centre of the collieries is 24 feet higher than Dr. 

 Burden's observatory, and is 216 feet above sea level. 



The first place of observation was in an exploring drift driven at a 

 high angle. The thermometer was placed in a hole in hard ' duns ' for 

 one week, and showed a temperature of 55 - 7. The depth was 441 feet, 

 and the hole partially filled with water from natural causes. The ther- 

 mometer was replaced, and after the lapse of another week the same 

 temperature was again found. 



The thermometer was next placed in a hard arenaceous stone yielding 

 a considerable quantity of water, at practically the same depth as the 

 last observation, and in the same drift. It gave a temperature 55*4. 



Under the stone, and resting upon the duns, was a seam of coal 

 averaging about 1 foot 6 inches thick, into which the thermometer was 

 next inserted, and 57'2 was read at the end of another week. Illness 

 prevented Mr. Wethered from making a re- examination to ascertain the 

 causes of the discrepancies here exhibited, and he therefore proposes to 

 reject these first observations. 



On the abandonment of the drift just referred to, the thermometer 

 was removed to a cross-measure branch, driven almost on a level. A 

 week or two before, a seam of coal about 2 feet thick had been cut in 

 this branch, and a level was now being driven on it. On Saturday, 

 June 15, a hole was bored, at the head of the level, in the coal, and the 

 thermometer inserted at 2 p.m., just as the men w£re leaving work. On 

 Monday the temperature 54" 7 was read. As the pit was idle on this day, 

 the thermometer was replaced, and after 12 hours gave the same reading. 

 The hole was perfectly dry, with the exception of what miners call 

 ' sweating.' 



On Saturday, June 23, the thermometer was placed in a hard blue 

 duns at the head of the cross-measure branch, 10 feet away from the last 

 hole ; and on Monday the temperature 54" 7 was taken, the same as in 

 the coal. The pit being again idle, the observation was repeated, with a 

 confirmatory result. The depth in each case was 402 feet. 



The next observation was in the deepest workings of the collieries, 

 in what is known as the Deep Pit colliery. A branch was being driven 

 for the purpose of cutting off an extent of road in the Great Seam workings ; 

 accordingly on Saturday, June 29, the thermometer was placed, in the 

 usual way, at the head of the branch in a blue duns ; depth 1767 feet. 

 On the Monday, 74' 7 was read, and this temperature was confirmed by an 

 observation from the following Saturday to Monday. 



The next observation was made at a higher level in the same pit, in 

 the Great Vein workings, depth 1367 feet. On Saturday, July 13, a hole 

 was bored in the same bed of duns as in the last observation, and on 

 the following Monday, 68"5 was read. 



On Saturday, July 20, the thermometer was placed in the Great Seam 

 coal, which rests upon the duns, and after the lapse of the usual time 67 - 5 

 was read. 



