250 Martinis Geological Memoir, and 



event, which cannot but be viewed as an interesting era in the 

 history of this branch of natural science, a considerable mass 

 of information was acquired by many naturalists, who entered 

 with avidity into a pursuit which combined the charms of 

 novelty and interesting discovery with the substantial advan- 

 tages of general utility. On all sides, fresh objects of wonder 

 and speculation presented themselves. Entire races of animals, 

 of unknown forms and singular adaptation, inhabitants of a 

 former world, but overwhelmed beneath its ruins, were found 

 to cover the earth with their remains, and were then first sub- 

 jected to the scrutiny of science. Amongst these were some 

 that could be recognised as resembling tribes peculiar to hot 

 climates, and they were found surrounded with the relics of 

 tropicar vegetation, with the palms, the cacti, the arborescent 

 ferns, and gigantic reeds of warm regions, all attesting the 

 changes which our planet had undergone. As the enquiry 

 proceeded, it became apparent that a degree of regularity 

 existed in these deposits, and that certain tribes or genera of 

 animals occupied particular members of the series of rocks. 

 Hence it was naturally suggested that these organic bodies 

 might be employed as indices of the several rocks or beds to 

 which they respectively appertained ; and their application has 

 proved of the utmost value, as permanent tests in identifying 

 the strata, when mineralogical characters are altogether un- 

 availing, or, at least, are doubtful evidence. The discovery of 

 these indices to the strata, led to a demonstration of the extent 

 and continuity of the various groups of which they are com- 

 prised, and thence to defining with precision the boundaries 

 of each description of rock, of earth, clay, or sand, and to 

 determining the superficial areas they successively occupied 

 after they rose to the surface. This extended acquaintance 

 with the geographical position of rocks, was accompanied by 

 a more accurate knowledge of their contents, as applicable to 

 the economy of man. We were thus enabled to avail our- 

 selves, with greater certainty, of the inestimable resources 

 contained within the bowels of the earth, and to avoid expenses 

 in useless pursuit of objects out of their natural limits. We 

 were also reasonably led to infer that the ultimate result of an 

 elaborate survey of the earth, if that process is not the only 

 one which conducts to a solution of the great problem, would 

 at least furnish safer ground on which to erect a theory of its 

 formation, and to speculate upon its antiquity, and the stupen- 

 dous revolutions to which it has been subjected. Our progress 

 towards the attainment of the latter objects, has apparently 

 iDeen much slower than our preliminary acquisition of the 

 data. But instances are by no means rare, where a thorough 



