Penny Blood: Serial Sensation and Working-Class Entertainment — page 13: what you’re looking at

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

x CONTENTS. CHAPTER XI. THE REVELATIONS OF THE PLUMB-LINE. Mountains the “backbones” of continents—They have ‘‘roots”—These are revealed by the plumb-line—Pratt’s calculation of the attraction of the Himalayas— The actual attraction less than that calculated—His attempted explanation of the discrepancy—Sir G. B. Airy’s explanation more satisfactory—Pratt’s reply shown to be inconclusive—The result confirms the reasoning of the preceding chapter—The plumb-line reveals a greater density beneath oceans . . ° . . . : : : : : : + 142 CHAPTER XII. THE REVELATIONS OF THE THERMOMETER. Recapitulation of results of previous chapter—Roots of mountains should be revealed by phenomena of underground temperature—Conditions upon which the mean rate of increase of temperature will depend—Rate greater in plains and less in mountains—Dr Stapffi—His observations on temperature of rocks in St Gothard tunnel—His explanation of the smallness of the rate—Why not satisfactory—Effect of convexity of mountain upon the rate—The rate may be considered uniform above—The conclusion from the premises is that the mountain has roots—The rate may be regarded as nearly uniform throughout —General method of determining the thickness of the crust at the sea-level, and the melting temperature, from the rates beneath the mountain and the usual rate—Application to St Gothard—Thickness of crust at sea-level and melting temperature deduced numerically from the data—The like for Mont Cenis—Results confirmatory of previous conclusions—Considerations about the oceanic areas—How the water is retained there—The thickness of the sub-oceanic crust and its density. ; : ; ° . ; . 151 CHAPTER XITI. AMOUNT OF COMPRESSION. Our ideas respecting the sub-oceanic crust necessarily speculative—Compression possibly confined to continental areas— Compression might arise from extrava- sation of matter from beneath the crust, or from expansion of the crust— ° Amount of compression needs to be estimated afresh—Datum-level equation transformed to mean level—Formula to express compression in terms of inequalities—Estimate of inequalities from Atlas—(1) Contraction on sup- position that Oceans are due to compression, (2) that they are due to denser (CO) commiclsoolkks