Penny Blood: Serial Sensation and Working-Class Entertainment — page 29: what you’re looking at

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

-_ I2 ON UNDERGROUND TEMPERATURE. [cH. I. In the discussions of these observations’ the observations made with the geo-thermometer have been in general looked upon as giving a near approximation to the temperature of the earth’s crust at this locality; and, consequently, it is these which we propose to consider further. Although the sixth column shows that the rate of increase of tempera- ture was far from equable when comparatively short inter- vals are taken into account, yet, when we pass to the eighth and ninth columns, we observe that on the whole there is a decided diminution of the rate of increase in the lower depths. It was probably this circumstance which induced M. Dunker to assume that empirical formula for the law of increase which led Prof. Mohr to believe that, at the depth of 5170 feet, the increase would be nil, and thence to conclude that the source of the heat of the crust must be situated within the crust itself, instead of—as is usually supposed—coming up from the pro- found depths below. The question which presents itself therefore (and it 1s a most important question) is—Can this diminution of the rate of increase in the indications of the geo- thermometer be consistent with an equable rate of increase in descending as deep as the observations went into the earth’s crust ? The answer, that it can, seems to follow from the considera- tions already made on the effect of convection currents upon the temperature, not of the water only, but of the rock itself. It is obvious that the continued contact of water at a different tempe- rature from that of the rock must alter the temperature of the rock itself where it is in contact with the water. And it has been remarked that, almost beyond dispute, it bad actually that effect; consequently the rock in contact with the water must have been cooled in the lower part of the bore-hole. Moreover, the principal cooling effect of the currents would occur towards the bottom of the hole, where the cold water coming down from above would tend to accumulate, because there would be no warm currents coming up from below to disturb it. When, therefore, we enquire how far the observations - 1 The writer has met with a course of lectures entitled ‘“ Vortriige iiber } Geologie, von F. Henrich, Wiesbaden, 1877,” in which the Sperenberg obser- vations are discussed with much acumen. COMIC OOOKS.EO @