Penny Blood: Serial Sensation and Working-Class Entertainment — page 34: what you’re looking at

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

CH. I.] ON UNDERGROUND TEM?PERATORE. 17 terranean course of the limestone is kept down by the imper- vious beds of the basin-shaped coal-measures, and reascending to the surface along the fault from which the springs are known to rise, brings with it the temperature of the rocks through which it has percolated. The temperature is 120°F,, which is 70° above what may be taken as the mean surface tem- perature, and would require, at the rate of one degree for fifty feet, a depth of 3500 feet to give the required increase. This is by no means an unlikely depth to be attained by the synclinal trough of the carboniferous limestone in Somerset. But the phenomena of volcanos, which are situated in all regions of the globe, and of which relics remain almost every- where among ancient rocks, point to an intensely high tem- perature at still greater depths. They afford however no clue as to what the depth may be from which their liquid ejecta- menta are derived without first assuming a law of temperature. Thus, it is a most important point to be borne in mind, that we know nothing by observation respecting the law of increase of temperature within the earth, beyond the facts that near the surface the average rate of increase 1s 1° F’. for between every 50 and 60 feet of descent, and that the temperature at greater, but unknown, depths is very high, and sufficient to fuse what, from that very cause, we term igneous rocks. This temperature cannot be lower than between 2000° and 3000° F., and may be:, much higher. But if an average rate of increase of 1°F. for e every 60 feet were to continue to all depths, the temperature in the interior would become enormous. In fact, at the depth of from 200 to 400 miles it would amount to from 18000° to 36000° F., which is what Prof. Rosetti has estimated from his experiments with the thermopile to be the probable temperature of the sun’. 1 His words are these: ‘‘I think then that I may fairly conclude that the true temperature of the Sun is not very different from its effective temperature ; and that it is not much less than ten thousand deyrees [cent.] if we only consider the absorption of the terrestrial atmosphere; nor much more than twenty thousand degrees if we also take into consideration the absorption by the solar atmosphere, estimating the latter at = 0 of the total radiation of the *Sun.” ‘** Phil, Mag.” Vol. vir. Fifth series, p. 550. . F. | 2 COLA @ NOO (CO)