30 REPORT— 1870. 



"We can feel no certainty that even the mean annual temperature in this 

 portion of the weU represents the temperature in the solid ground. On the 

 contrary, the mean temperature in the weU at any depth is probably inter- 

 mediate between the temperature of the solid ground at that depth and the 

 mean temperature of the external air. 



It is well that such observations should have been carefully made and re- 

 corded in this one instance, if only for the sake of warning ; and they show 

 that we cannot expect to attain the object for which the Committee has been 

 appointed by observations in large shafts filled with air. 



Mr. Symons has also repeated the observations at 250 feet (which is 40 feet 

 under water), and at the depths of 600 feet, 750 feet, and every 50th foot 

 from this to 1100 feet, the lowest point attainable, on account of the mud, 

 which extends 200 feet lower. The differences from the results obtained last 

 year are +-2, --3, —-4, —-2, —-2,0, -•!, — -1, 0; which upon the whole 

 strongly coufia-m the correctness of the observations. 



The temperature at 1100 feet is 69°-8, which, if we assume the mean tem- 



f 50° 

 perature of the surface of the ground to be < ,go, gives a mean increase 



t 'Ol 5^0 r 55*5 



downwards of < .n-ioq of a degree Fahrenheit per foot, or 1° for j ^2-9 ^^®^- 



The curve in which temperature is the ordinate and depth the abscissa, ex- 

 hibits considerable irregularities tUl we reach the depth of 650 feet, beyond 

 which it is nearly a straight line, and represents an increase of -0187 of a de- 

 gree per foot. 



The strata penetrated by the weU to the depth to which our observations 

 extend consist of clay, sand, chalk, and marl, besides flints. (See tabular 

 list appended.) 



Mr. Symons in his Eeport calls attention to the anomalous position of a 

 column of water increasing in temperature and consequently diminishing in 

 specific gravity downwards, and suggests the inquiry why the warmer and 

 lighter portions do not ascend to the top. The proper reply seems to be that 

 the diminution of specific gravity, amounting to less than 1 part in 50,000 

 per vertical foot, does not furnish sufiicient force to overcome liquid adhesion, 

 and the water is thus able to remain in unstable equilibrium. 



Mr. Symons intends, during the remainder of the present year, verifying 

 those of his observations which have not yet been repeated, and concludes 

 his Report by remarking that it appears desirable to ascertain, by observa- 

 tions from year to year, whether the temperature at a given depth (say, 

 1000 feet) remains constant or is subject to minute changes periodical or 

 otherwise — a suggestion which appears fully worthy of being carried out. 



Mr. Wm. Bryham, Manager of Eose Bridge Colliery, Ince, near Wigan, 

 has taken very valuable observations during the sinking of that CoUiery, 

 which is now the deepest excavation in Great Britain. The pricipal results 

 have already been given, in a paper to the Royal Society, by Mr. Edward Hull, 

 Director of the Geological Survey of Ireland, who had previously published 

 some important contributions to our knowledge of underground temperature, 

 and has now consented to become a member of this Committee. Some of 

 the depths, however, have been remeasured since Mr. Hull's paper was read, 

 and I am now enabled, through the kindness of Mr. Bryham, to furnish a 

 rather more accurate report. 



The temperatures observed and the depths at which they were taken are 

 as follows : — 



