633 



matter of course ; and thus showed the wisdom of separately cultiva- 

 ting the study of causes, and the classification of facts. 



DESCRIPTIVE Geology. 



If we begin with geological facts, our attention is first drawn to 

 that district on the earth's surface within which the facts have been 

 subjected to a satisfactory comparison and classification, which may 

 be considered, in a general way, as including England, France, Italy, 

 Germany, and Scandinavia. The language which the rocks of these 

 various countries speak has been, in a great measure, reduced to the 

 same geological alphabet. The questions of the determination of 

 any member in one country, or the identification of similar members 

 in two countries, are, for the most part, problems admitting of a defi- 

 nite and exact solution. I^ countries out of this district, on the 

 other hand, we have not only to explore but to classify. We have 

 to divine their geological alphabet ; — to decipher as well as to read. 

 We have not only to discover of what British rocks the observed 

 ones are the equivalents, but we have to ascertain whether there 

 be an equivalence ; and where this relation vanishes, we have to 

 discover what new resemblances and diiferences of members are most 

 worthy our notice. The great difference in the nature of the geologist's 

 task in these two cases seems to me to make it desirable to employ 

 the familiar division oi Home and Foreign Geology in a wider sense 

 than has hitherto been common, including in the former aU that re- 

 gion of Europe which has had its order of strata well identified with 

 our own ; this distinction then I shall employ. 



1. Home (North European) Geology. — If we attempt, in this part of 

 our subject, to follow an order of strata, we must begin with the 

 oldest stratified rocks, though they are undoubtedly the most ob- 

 scure ; for the same reason which compels the historian of states to 

 begin with the dim twilight of their savage or heroic times ; namely, 

 because at the other extremity of the series there is no boundary ; 

 since the events of past ages and their records form an unbroken 

 series, leading us to the unfinished occurrences and works of to-day. 

 Going then as far back as the historian of the earth can discern any 

 light, and, for reasons which may hereafter be spoken of, shaping our 

 course by the stratified rocks alone, we should first have to ask what 

 addition has been made during the past year to our acquaintance 



