Penny Blood: Serial Sensation and Working-Class Entertainment — page 33: what you’re looking at

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

16 ON UNDERGROUND TEMPERATURE. [cH. I. convection currents full play, the temperatures taken at the lower parts will—even with the geo-thermometer—be less than the true rock temperature. The conclusion appears a legitimate one that the diminution in the rate of increase in a bore-hole, even when the convection currents are temporarily shut off, does not necessarily imply that there is any such diminution of the rate in the body of the rock; or, in other words, that the temperature curve within the rock may be a straight line, although that given by the geo-thermometer be concave to the axis of depths. It will also follow that the mean rate of increase for the whole depth within the rock will exceed that shown by the geo-thermometer. The mean increase, for instance, in the above table, between the temperature of the surface and that at 4042 feet,is 1° R. for 129 feet, or 1° F. for 57 feet; and it is stated in the Association Report that, when the observations are corrected for pressure, the mean rate to 3390 feet is 1° F. for 51:5 English feet. This is about the usual average. We may therefore conclude that at Sperenberg the actual rate of increase in the body of the rock is greater than this, The most important conclusion from the above is that, in spite of the decreasing rate shown at Sperenberg (and also at St Louis, and perhaps other places), the old assumption is pro- bably correct, that for such depths as have been reached, the rate—if it could be truly observed, and setting aside local causes - of disturbance—is probably a uniform rate, amounting to, or, as the above reasoning would lead us to infer, rather exceeding, 1’ F. for 51 feet of descent. And this is all that we know ex- perimentally respecting the rate of increase of temperature within the earth. We have reason, however, to believe that at still greater depths the temperature continues to increase, . because many thermal springs deliver water at the surface at a much higher temperature than has been reached by any artificial perforations. And yet the waters yielded by Artesian wells ‘are in their degree thermal springs, so that the hotter natural springs, such at least as are not obviously situated in volcanic regions, are probably exactly in the same category as the deeper Artesian wells. For instance, it appears extremely probable that the Bath waters are simply springs supplied by the rainfall on the Mendip hills. The water following the sub- COMIC OOOKS.EO