70 Analyses of Books. 



Such is a general view of the contents of the first volume. It 

 commences with an introduction explanatory of the nomenclature of 

 the external characters of minerals, and exhibiting a view of the 

 system of crystallography adopted by Mohs, for the purpose of en- 

 abling the English reader to consult Haidinger's admirable transla- 

 tion of Mohs' works. The volume concludes with three tables, in 

 the first of which are given the specific gravity, hardness, and form 

 of the crystals of minerals, in the order of the chemical arrangement. 

 The second affords a list of minerals arranged according to the spe- 

 cific gravity, beginning with Scheererite the lightest ; and the third 

 supplies a list of minerals in the order of their hardness. Mineralo- 

 gists will at once appreciate the utility of these tables. 



The first 345 pages of the second volume are devoted to an outline 

 of geology, and a valuable and complete table of the fossils, plants, 

 and animals found in the mineral kingdom. 



The first chapter, on the Temperature of the Earth, is full of most 

 important matter. In order to determine the state of the question 

 in reference to the existence of a central fire, the author has collected 

 iill'the observations that have hitherto been published on the tem- 

 peratures, from the surface of the earth to the greatest depth that 

 has been attained by man. From these it appears that, taking the 

 mean of nineteen observations, there is an increase of 1° F. for every 

 50 feet of descent. This is the evidence which many bring forward 

 for the existence of a central fire. The author, however, shews, that 

 according to the observations of Mr. Movie, made during a series of 

 years in Cornwall, the high temperature of these mines continues 

 only while they are working. When they are abandoned they are 

 soon filled with water, which remains stagnant, and the temperature 

 gradually sinks, till it approaches that of the mean temperature of 

 the place. 2. That the temperature of the earth is regulated en- 

 tirely by the sun, for, the higher the sun is elevated above the 

 horizon and the longer it continues above the horizon, the higher is 

 the temperature. If the temperature increased 1° for every 50 feet, 

 a descent of 12 miles, or a point by so much nearer the centre 

 of the earth than the position of the equator, should afford a tem- 

 perature, allowing for radiation, of 1200°. Now, this ought to be 

 the temperature of the poles, because they are 12 miles nearer the 

 earth's centre than the equator. Their temperature is, however, 

 — 13°, and hence, this seems a fatal argument to the notion of a 

 central fire. But, although the idea of a central fire is not supported 

 by the facts with which we are acquainted, it is not unlikely that an 

 internal fire exists, which gives origin to those vast volcanic regions 

 and earthquakes which are continually altering the aspect of the earth's 

 surface. If we were to consider this fire as approaching nearer the 

 surface in some places than in others, we might have, perhaps, an 

 explanation of the relative causes of volcanoes and earthquakes. 



The remainder of the geological portion is divided according to 

 the formations, beginning at the surface. Many original observations 

 are detailed, especially in reference to the geology of Scotland, where 

 the occurrence of most remarkable alterations in the relative levels 

 of the sea and land is minutely detailed. The Glasgow coal beds 



