1.88 Rev.W. D. Conybeare on the Phenomena of Otology 



will be freed from all pressure caused by the attraction of the 

 exterior matter, if the stratum exert no attractive force upon 

 the particles situated in its lower surface; and this property, 

 more general than the other, is indispensably required for the 

 equilibrium. The paper alluded to must therefore be cor- 

 rected by substituting the second property in place of the first; 

 for which purpose nothing more is necessary than a change of 

 the language in some parts, without any alteration of the cal- 

 culations or the results. 



In a homogeneous fluid in equilibrium it may be proved 

 that the whole matter above any level surface must act upon 

 the fluid below it by external pressure only, without exerting 

 any accelerating force upon the particles that may cause in- 

 ternal pressure : and, as this is general whatever be the nature 

 of the accelerating forces, it may properly enough be called a 

 new principle of hydrostatics. 



The embarrassment attending the application of Clairaut's 

 theory arises from that author having failed to lay down the 

 independent conditions of the equilibrium. Of the two con- 

 ditions which are asserted to be necessary and sufficient for 

 the equilibrium, one is included in the other : for it is easy to 

 prove that the equation of the outer surface is deducible from 

 the other condition. 



Feb. 12, 1831. JAMES IVORY. 



XXXV. An Examination of those Phenomena of Geology, 

 which seem to bear most directly on theoretical Speculations. 

 By the Rev. W. D. CONYBEARE, M.A. F.R.S. F.G.S. $c. 



[Continued from page 116.] 



Part the Second. Of Aqueous Action, and the excavating 

 Forces which have operated on the Strata. 



HPHE phenomena of geology (to assign an adequate cause 

 * for which, is the legitimate aim of theory) appear to me 

 reducible to two classes: 1. those which indicate igneous 

 action and the operation of elevating and dislocating forces 

 on the strata; and, 2. those which indicate aqueous action 

 and the operation of excavating forces. My former observa- 

 tions, which I would consider as constituting the first part of 

 my present essay, have been dedicated to the first class of 

 these phaenomena ; and I now propose to enter on the second. 

 On these two heads, the difference between Mr. Lyell and 

 myself amounts simply to this : Mr. Lyell believes that the 

 forces which act on our planet have been, and are, ever con- 

 stant and invariable ; that therefore as to the first topic, all 



the 



