JRevietos — Skertchly's Physical System of the Universe. 83 



lost sight of, for as early as 1849 a little work entitled " The Unity 

 of Nature," by John Wan-en Howell (edited by Charles Pooley), was 

 published; a work whose object was to show the relation of the 

 sciences one to another. But recent spectroscopic observations have 

 especially led to the conclusion that all the heavenly bodies " are 

 but parts of one stupendous whole." 



In the work now before us, Mr. Skertchly gives us an outline of 

 physiography, embracing all the latest work in astronomy and 

 physical science which bears upon the history of the universe. It is, 

 we must premise, a work which contains a good deal of hard reading, 

 and perhaps too many technical terms to please an ordinary 

 reader. In the introductory chapter the author briefly sketches the 

 plan of his work, and shows that the past and present state of the 

 globe are the result of the action of heat upon solid, liquid, and gaseous 

 matter. Chapter 2 deals with Matter and Motion, and it is pointed 

 out that the earth is not an isolated fragment in space, but part of 

 one great machine. Chapter 3 treats of Light and its Revelations, 

 and it is shown that the sun, stars, etc., contain the same elements 

 known to us on earth. Chapter 4 is devoted to the Sidereal System 

 — a term applied to the whole of the visible universe, with its hosts of 

 stars, nebulae, etc., and it is pointed out that not only is it composed 

 of the same kind of matter, but this is acted upon by the same laws 

 as terrestrial matter. In Chapters 5, 6, and 7, the Solar System 

 is treated ; the motions, reactions, and influences of the bodies are 

 dwelt upon, also the oi*igin and movements of meteors and comets. 

 Chapter 8 is devoted to the Sun, and all that is known of it — the 

 influence of the cycle of its spots on terrestrial magnetism, tempe- 

 rature, rainfall, and other phenomena. Chapter 9 deals with the 

 Earth's Internal Heat, in which it is concluded that the interior is 

 probably metallic; that, as a whole, the earth is very rigid, and 

 cannot be molten in the interior ; that it contains great cavernous 

 spaces more or less full of liquid rock ; and that volcanic action has 

 been far more extensive than it is at present. The effects of In- 

 ternal Heat and influence on the production of faults and contortions, 

 upheavals and depressions, and in the sketching out of the broad 

 features of the continents are noticed in Chapter 10. The effects of the 

 Earth's External Heat are pointed out in Chapter 11, where various 

 climatic conditions are shown to result from Solar Heat. Chapter 

 12 continues this subject in its bearing on Earth Sculpture, where the 

 influence of Subaerial Denudation is noted as the most prominent. In 

 Chapter 13 the subject of Climate is again dealt with, also the causes 

 of great variations in past periods. The conclusions being that cold 

 and warm periods alternated in comparatively rapid succession during 

 the Glacial period ; and that they are due to the indirect results of a 

 high excentricity, combined with the position of the solstitial points 

 in aphelion and perihelion. Chapter 14 deals briefly with Life, 

 and it is shown how dependent the forms and their distribution are 

 upon climatic change. The concluding chapter discusses the Nebular 

 Hypothesis, which, while it is stated to be the natural explanation 

 of the Solar system, yet is not supported by what is known of exist- 



