492 
THE INFERIOR TEMPERATURE OF; THE EARTH. 
at the law of its distribution,it was deem- 
ed a matter of much importance to get 
rid altogether of the effect of the air’s 
temperature upon the thermometer, as 
also the action of water, because the 
sources of the water in mines, &c. must be 
in most cases entirelybeyond the reach 
of observation. All these circumstances 
induced the Committee appointed by the 
Association to conduct experiments upon 
this subject, to take the temperatures 
of the rocks themselves alone, as the 
fundamental experiments. With this 
view, they had no less than thirty-six 
thermometers made arid carefully com- 
pared ; and, although they well knew 
that these thermometers, after all the 
care which had been bestowed upon 
their construction, were by no means 
perfect or exact, yet as their errors had 
been carefully quoted, by a comparison 
with the standard thermometers of the 
Ro)^al Societies of London and Edin- 
burgh, and each thermometer numbered, 
the errors admit of an easy correction. 
Many of these thermometers had been 
already placed under the care of persons 
adequately instructed to conduct the re- 
quisite experiments, and some of them 
were still in the possession of the Com- 
mittee, who would gladly place them in 
the charge of any person, giving adequate 
security that they should be applied to 
the purpose for which they had been 
procured. The method of using them 
was this; a hole large enough to receive 
one of the thermometers, is first drilled 
into the solid rock, at the bottom of the 
mine, pit, or other proper place of obser- 
vation, to the depth of two or three feet 
at least ; into this the thermometer is 
then introduced and sutfered there to 
remain for a number of days sufficient to 
ensure the attainment of the temperature 
of the rock itself. The temperature of 
the air at the mouth of the pit,* and if 
possible, the mean temperature of the 
place, must be observed or obtained. 
Professor Phillips then stated, that ob- 
servations had been made in this man- 
ner, and with some of these instruments, 
under the directions of Professor Forbes, 
at mines in the Lead Hills, in Scotland, 
• It appears to us that it would be most disir- 
able that the temperature of the air at the 
bottom of the pit, and as close aspossiiile to 
the rock in which the thermometer is placed, 
«hould be noted, for unquestionably this are 
cannot be excluded from the hole in which the 
thermometer is placed, and must have an ele- 
vated temperature . 
and that Professor Forbes would >ako 
some early opportunity of bringing these 
observations more immediately under 
the notice of the Section ; at Newcastle, 
under the direction of Mr. Briddle; at 
W^earrnouth, under the care of Mr. 
Anderson; near Manchester, and at 
Northampton, under the direction of 
Mr. Hodgkinson : and -within a few 
days. Professor Phillips had been ena- 
bled, through the kindness of a friend, 
to place a thermometer in a deep coal 
mine at Bedminster, in this immediate 
vicinity (Bristol). The results of these 
observations, so far as they had as yet 
proceeded, amply confirmed the fact of i 
the increase of temperature in the parts 
under the earth’s surface. As one ex- 
ample, the Professor stated, that in a 
mine, the perpendicular depth of which, 
below the surface, was 525 yards, the 
thermometer in the rock stood at 7^“, 
while the temperature in the open air at 
the mouth of the mine, varied from 300 
to 800, the mean temperature of the 
place being 47^®. 
Professor Forbes then gave, from me- 
mory, an account of the experiments which 
he had been the means of instituting in 
the Lead Hills. Before he did so, however, 
he w'ished to state that he had been in- 
formed that an artesian well had lately 
been met with in granite ; and he then 
gave a general description of artesian 
wells. It was to this effect : that here- 
tofore, in making borings in certain 
districts through certain alternations of 
clays, and at length through certain 
rocks, a supply of water was reached, 
which rapidly rose through the boring 
to the surface, and continued to over- 
flow at the top, sometimes, as the term 
fountain indicated, in considerable quan- 
tity, and with considerable force. He 
instanced the artesian wells or fountains 
of the London clay districts; and added 
that the temperature of these waters 
was found universally to increase with 
the depth of their source beneath the 
surface of the earth. Heretofore, no 
such well had been obtained by boring 
through the granite ; and if the account, 
which he had received, were correct, 
and of its correctness he entertained 
little doubt, this would be a matter of 
considerable interest as well to the geo- 
logist as to those who were engaged in 
scientific pursuits similar to those now 
under consideration. The observations 
made under his directions in the Lead 
