516 Progress of Geological Science. [Nov. 



first of these connections, the Rev. Professor Sedgwick thus states the actual 

 state of opinions. 



" Some great and simple problems in physics have so immediate a connexion with 

 the structure of the earth, that we may almost claim their solutions for our own. 



" The form put on by a fluid body in rotation is an abstract question, which might 

 or mi»ht not have any real application to the bodies of our solar system. But direct 

 geodesic observations, as well as the relative position of land and water, prove 

 that the stratified matter on the crust of the earth is deposited in near conformity 

 to the surface of a true spheroid of rotation. Here then we have, in spite of one 

 of the arbitrary dogmas of the Huttonian theory, an indication of a primeval fluid- 

 ity before the commencement of any one phaenomenon coming within the direct 

 speculations of geology. And again, the direct phenomena of geology are in the 

 strictest harmony with this conclusion. For, after passing through a few stages 

 of stratified matter, formed by the degradation of matter in a prior state of soli- 

 dity we are conducted to other unstratified masses with that crystalline structure 

 which implies an anterior fluidity — in some cases unequivocally, and in all cases 

 probably, derived from the solvent power of heat. 



" But if the earth ever existed in any state approaching to igneous fusion, it must 

 have undergone a great diminution of temperature, before it was fitted for the 

 habitation of any organized being. And here again geological facts are at least 

 in a general accordance with the hypothesis ; for the forms of the living beings, 

 entombed among the ancient strata, not only seem to indicate a high temperature, 

 but also a gradual refrigeration of the surface of the earth. 



" Here however we meet with an unexpected difficulty. If during any period, the 

 earth have undergone a sensible refrigeration, it must also have undergone a con- 

 traction of its dimensions ; and also, as a necessary consequence of a well known 

 mechanical law, an acceleration round its axis of rotation. But direct astrono- 

 mical observations prove, that there has been no sensible diurnal acceleration 

 during the last 2000 years ; and therefore, by inverting the steps of the reasoning, 

 we prove — that during that long period there has been no sensible diminution in 

 the mean temperature of the earth. This difficulty does not, however, entirely 

 upset the previous hypothesis : it only proves, that the earth had reached an equi- 

 librium of mean temperature before the commencement of good astronomical 

 observations. 



" But if our speculations are thus limited and guided by the observations of as- 

 tronomy, we have in part paid back to that exalted science the obligations we 

 owe to it. The great bodies of our system leave behind them no marks to track 

 their progress through the heavens ; and the vast secular periods we can cal- 

 culate, reaching to ages long anterior to the records of our being, might be 

 mere fictions of the mind, which have never had any archetype in nature. But 

 in the phaenomena of geology, we are carried back, almost at our first step, into 

 tiroes unlimited by any narrow measures of our own ; and we exhibit and arrange 

 the monuments of former revolutions, requiring for their accomplishment perhaps 

 all the secular periods of astronomy. Nor is this all. We show, by help of records, 

 not to be misinterpreted, that during this vast lapse of time, in the very contem- 

 plation of which our minds become bewildered, the law of gravitation underwent 

 no change, and the powers of atomic combination were still performing their office. 



" If the phaenomena of geology be coeval with long returning astronomical pe- 

 riods (and it is at least impossible to prove the contrary), a question may arise, 



