2,20 Geological Society, 



not necessarily the effect of disturbance, but are to be attributed, in 

 the Primary Slates, to original structure, and in many of the Second- 

 ary, partly to this cause, and partly to deposition upon inclined sur- 

 faces. 



The difficulty I have been considering is by no means confined to 

 Primary Slates. Mr. Conybeare has observed on the coast of Sully, 

 in Glamorganshire, that the Lias splits spontaneously into blocks of 

 regular figure, corresponding to that of a crystal of calcareous spar. 

 If this be the case, where are we to look for the seams of Stratifica- 

 tion ? I have felt for very many years, and I still feel, that the 

 indistinctness of this term is one of the most dangerous stumbling- 

 blocks we have to encounter. If we would found upon this distinc- 

 tion the grand classification of rocks into Neptunian and Plutonic, 

 surely we ought to have some test by which to determine whether 

 rocks are stratified or not. If, looking to the theory of M. Elie de 

 Beaumont, we would know whether strata are conformable or dis- 

 turbed, surely we ought to be placed in a condition to determine 

 what Strata are. On taking leave, as I must do, of Dr. Boase's work, 

 I again recommend it to your attentive perusal ; it is written with 

 great candour as well as earnestness, and will be found a useful cor- 

 rective of many opinions which appear, to me at least, to have been 

 too inconsiderately adopted. 



Mr. De la Beche, one of your Vice-Presidents, to whose pen and 

 pencil our science has been for a series of years continually and largely 

 indebted, has published a small volume, entitled " Researches in Theo- 

 retical Geology". The main tendency of this volume is to establish 

 the importance and practicability of subjecting geological opinions to 

 the tests of chemistry and natural philosophy. The Author goes over 

 much ground, keeping always the same direction, having apparently 

 no other objects in view than the acquisition and communication of 

 sound knowledge, the detection and exposure of error, and the disco- 

 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, 

 silicium, 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 



