Penny Blood: Serial Sensation and Working-Class Entertainment — page 284: what you’re looking at

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

CHAPTER XXII. SUMMARY. [The Roman numerals refer to the Chapters.) I. On underground temperature—II. Condition of interior—III. Internal den- sities and pressures—IV. Lateral pressure, its amount—Y. Elevations and depressions—VI. Elevations on the hypothesis of solidity—VIL. Hypothesis of solidity fails—VIIIL. Fluid substratum—IX. Crust not flexible—X. Dis- turbed tract—XI. The revelations of the plumbline—XIIL. The revelations of the thermometer—XIII. Amount of compression—XIV. Extravasation of water will not account for compression—XVYV. Compression and volcanic action—XVI, On Faulting—XVII. Geological movements explained — XVII. Mr Mallet’s theory of volcanic energy—XIX. The volcano in eruption—XX. Sequence of volcanic rocks—XXI. Geographical distribution of volcanos. I. WE have commenced our discussion of the wide subject of the Physics of the Earth’s Crust with underground tempera- ture, because the distribution of heat in the interior of the earth is one of the cardinal conditions upon which all physical questions connected with it depend. We have pointed out that, having regard to such depths as artificial excavations reach, the law of increase is on the whole an equable one, amounting on an average to about one degree Fahrenheit for every 51 degrees of descent. It has been asserted that the rate has been found to decrease towards the bottom of some deep boreholes, and it has been even maintained that at a depth of about 5000 feet the increase of temperature would come to an end. But we have shown reasons for believing, that the observations, in which a diminution in the rate has been said to have been noticed, have really been vitiated by the disturbance of the column of water in the borehole by convection currents, and that the supposed cessation of the increase at about 5000 feet has arisen from a delusive method of computing the general result. Neverthe- less it 1s unquestionable that this equable law of increase of temperature, though probably true near the surface of the earth, cannot extend to all depths; for, if it did, we should COMMUC NOO (CO)