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very and establishment of truth. Unshackled by authority, unen^- 

 slaved by preconceived opinions, unseduced by the love of novelty, 

 free from all vanity of authorship, concise, methodical, exercising his 

 judgement continually, his fancy seldom, the author may not obtain 

 that popularity which with less merit he might have easily commanded ; 

 but such a work cannot fail to be appreciated here. 



After taking a general view of the Solar System, and considering cer- 

 tain apparent agreements and disagreements in the condition of some 

 of the Planets, Mr.de la Beche applies his observations entirely to the 

 Earth, which he supposes to have been originally in such a state that 

 its component particles had a free passage among one another. The 

 principal Constituents of Land, Water, and Air, sixteen in number, 

 are made up of Substances commonly termed simple: viz. oxygen, 

 hydrogen, nitrogen, carbon, sulphur, chlorine, fluorine, phosphorus, 

 sillcium, aluminum, potassium, sodium, magnesium, calcium, iron and 

 manganese. Adopting Laplace's hypothesis, that the sun, planets, 

 and their satellites, have resulted from the Condensation of gaseous 

 matter, he ascribes the Condensation of our own planet to the gra- 

 dual Radiation of Heat into space. He shows how Sedimentary Rocks 

 may be deposited so as to present, from the first, inclined planes, and 

 that we should therefore be cautious in referring to subsequent dis- 

 placement all deviations from a horizontal level : he forms an esti- 

 mate of the Destruction of Land by Breakers, of the wear and tear 

 of Running Waters, of the transport of detritus by Rivers. 



The mean Density of the crust of the earth is usually reckoned at 

 2*5. From a reference to the lists, which the author has drawn out, 

 of the specific gravities of many rocks, of the various simple minerals 

 which enter into their composition, and of certain recent shells, it 

 would seem that 2'6 would be nearer the truth. 



The Author investigates the Chemical Changes which Rocks undergo 

 after their formation, and the subject of Concretions, such as Ludus 

 Helmontii, &c. He remarks on the importance of attending to the 

 Cleavage of Rocks, whether igneous or aqueous, and their Transforma- 

 tion : he considers the great Breaks of the Surface in reference to the 

 effect which would result from its gradual cooling; and, from the con- 

 tortions and Fractures of Mountain Chains, infers the Intensity of the 

 forces that have acted upon them : he shows that certain Thermal 

 Springs may be occasioned by the Condensation of volcanic discharges 

 of gas and vapour, and ascribes the Uniformity of their Temperature 

 to the Constancy of such condensation : he then treats of Volcanic 

 Action and the gradual Rise of large tracts of Land. 



When explaining the Formation of Valleys, Mr. De la Beche con- 

 tends that the " Bursting of Lakes," as it has been termed, could not 

 take place in the way supposed. The Area, comprised within sound- 

 ings, that is, within the 100 fathom line, round the British islands, is 

 delineated on a map, in order to show, that within that area at least, 

 no Valleys are produced by Tides and Currents ; whence it would fol- 

 low, that such effects cannot be satisfactorily referred to such causes. 

 Under the head of Faults, which are treated of at some length, the 

 author shows with what facility " Craters of Elevation" may be formed^ 



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