Physical Properties of the Materials of the Earth's Interior

XXII. Researches in terrestrial physics.-Part II

Philosophical Transactions of the Royal Society of London ◽

10.1098/rstl.1851.0025 ◽

1851 ◽

Vol 141 ◽

pp. 511-547

Keyword(s):

Physical Properties ◽

Crystalline State ◽

Fundamental Importance ◽

Interior Structure ◽

Geological History ◽

Experimental Knowledge ◽

Physical Evidence ◽

The Earth ◽

Earth’S Interior ◽

Earth's Interior

In the first part of these researches, I have endeavoured, by generalizing the hypothesis on which is usually founded the theory of the earth’s figure, not only to improve that theory, but also to establish a secure basis for researches into the changes which may have taken place within and at the surface of the earth during the epochs of its geological history. Although I stated that no precise physical evidence could be adduced for the examination of the assumption that the molecules of the primitive fluid, supposed to have constituted the earth, retained their positions after solidification, it yet appears that such evidence exists, if we may be permitted to draw any conclusions relative to the physical properties of substances in the earth’s interior, from the observed physical properties of substances at its surface. Professor Bischof of Bonn, has shown that Granite contracts in volume in passing from the fluid to the solid crystalline state, from 1 to ⋅7481, Trachyte from 1 to ⋅8187, and Basalt from 1 to ⋅8960. The first of these rocks appears, as far as can be observed, to constitute the greater part of the earth; hence the assumption alluded to must be considered not only as superfluous, but as erroneous. In this Part it is my object to discover relations between the interior structure of the earth and phenomena observed at its surface, and also the effects of the reaction of the fluid nucleus, described in Article 6, Part I., upon the solid crust. I divide this Part into sections, each containing a distinct investigation, the order of arrangement of these sections being determined according to their fundamental importance. The statement of the geological results capable of being deduced from these investigations is, for greater clearness, reserved for the end. Such of these results as chiefly depend on the validity of the reasonings used in Section III. are presented with some diffidence, owing to the imperfect experimental knowledge we possess respecting the subjects discussed in that section. The diminution of the earth’s mean radius by refrigeration is neglected all through, except where the contrary is specially mentioned.

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