Penny Blood: Serial Sensation and Working-Class Entertainment — page 32: what you’re looking at

Machine-transcribed from the original scan — historical spelling and the odd misread are preserved.

CH... | ON UNDERGROUND TEMPERATURE. 15 ordinary rock, so that the heat would pass more quickly through it’, yet there will be a compensating effect in the present instance, because, on account of the greater conductivity, the true rock temperature would not be reached within so small a distance from the bore-hole, so that the heat would have a longer distance to travel before the true temperature could be restored. That the geo-thermometer was not left in place sufficiently long for this purpose seems to be proved by the following instance of the extreme slowness with which the passage of heat under such circumstances takes place. From comparing the British Association Reports for 1872 and 1873 we gather that, in the course of the observations made at the Artesian well of La Chapelle, at St Denis, 1t was noticed that the temperature at the hottom of the hole was much affected by the action of the “trepan” or boring tool. It appears to have been expected that this effect would have passed off in a few days. Accordingly, a week after the tool was stopped, observa- tions were taken, and there was found what was thought to be an unaccountably sudden increase of nearly 8° F., in 60 feet of descent, near the bottom of the hole. But in the following year a second set of observations were made “some months” after the boring had been suspended, and the abnormal increase was found to have entirely disappeared. We learn, then, that a week was not sufficient for the rock wall of the bore-hole to regain its balance of temperature after having been disturbed through about 7° F. How much longer was required we have not the means of knowing. It seems a necessary inference that a few hours would be quite insufficient for a correct observation, and the time allowed at Sperenberg did not exceed such an interval. The conclusion must therefore follow that, on both the accounts referred to, the geo-thermometer must have shown. in the lower depths a temperature less than the true tempe- rature of the rock of the earth’s crust existing at that depth. The reasons given above seem quite sufficient to account for the diminished rate of increase of temperature shown in the table; and they would lead to the conclusion that in all ob- servations made in bore-holes of a sufficient width to allow 1 This however is doubtful, for if it were so, the rate of increase ought to have been less than the normal rate. Such was not the case. See note, p. 5. GONG oOo SS (CO)