Penny Blood: Serial Sensation and Working-Class Entertainment — page 22: what you’re looking at

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

CH, 1.] ON UNDERGROUND TEMPERATCRE. 5 perature of the water which is obtained on lowering a thermo- meter into it, and we cannot be sure that that coincides with the temperature of the rock. In fact many reasons may be assigned why it should not do so, Springs may enter on one side and flow out at the other; or they may rise from lower levels and flow away at higher. The very act of lowering the thermometer tends to mix up the differently heated layers of water, and to confuse the result. A single instance will suffice to illustrate the irregularity of increase referred to. At Rose Bridge Colliery the temperatures were taken by drilling a hole a yard deep at the bottom of the shaft during the process of sinking. If the mean temperature of the surface there be taken at 50° F., the mean rate of increase for the whole depth was 1 degree for 55 feet. But at the suc- cessive depths of 605, 680, 663, 671, 679, 734, 745, 761, 775, 783, 800, 806, 815 yards respectively the rate appears to have been 1 degree for 70, 25, 49, 24, 24, 110, 66, 32, 42, 48, 51, 36, 54 feet. Within the last few years a very deep boring has been carried down at Sperenberg, near Berlin. This has reached the extraordinary depth of 4052 Rhenish feet, or 4172 British feet. A most surprising geological fact about this boring is that, with the exception of the first 283 feet, which were carried through gypsum with some anhydrite, the remainder passed entirely through rock salt. This seemed to offer an exception- ally good opportunity for observing temperatures in a homo- geneous rock, which might be expected to be comparatively free from the sources of error arising from variable heat-conducting power in the layers successively penetrated’. The observations 1 If F be the flow of heat from below, «x the conductivity of the rock, v the temperature, and x the depth, then Pace, Now the flow of heat at depths beyond the reach of the influence of the seasons will be the same for moderate depths, or F is constant, and ~ gives the increase per foot of descent. Hence = =< shows that the increase of temperature per foot is inversely proportional to the conductivity of the rock, so that where the rock conducts heat badly the increase will be more rapid, and vice vers@- COLA @ NOO (CO)