302 M. D'Omalius D'Halloy on a 



from the disposal and elevation of the soil, from the forma- 

 tion of the valleys, and the existence of some superficial 

 deposites, all these rocks present tlie same aspect, the same 

 tendency to be covered with heaths, pastures, or forests, and 

 the same difficulty of producing wheat ; characters which 

 are found equally on the slates of the Ardenne, the granites 

 of the Limousin, and the talcose rocks of the Alps. 



The secondary rocks do not offer the same uncertainty as 

 the primordial, tlie superpositions are here evident, and al- 

 though a part of tliem have suffered the effects of distur- 

 bance, it is not in so violent or irregular a manner, and we 

 cannot here suppose that a large mass has really been turned 

 over ; the very general presence of organic remains offers 

 many means of comparison between distant countries, espe- 

 cially since the brilliant progress this study has made of late 

 years. Yet, the distribution of the liquids into particular 

 basins in which the newest formations have been deposited, 

 the tendency that these rocks have to change their aspect 

 or rather to develope one system at the expense of another, 

 according to countries, leave many doubts to be cleared up. 



I have considered myself able to divide these rocks into 

 five groups, of whicli I shall sketch tl\e general characters. 



The first has for its type the rocks known in German geo- 

 logy by the name of todt-liegende* or red sandstone, to 

 which I unite the macigno of the Tuscans, + and many coal 

 measures, particularly those of the centre of France. J 



* The new red sandstone conglomerate of Devonshire, &c. (Trans). 



+ A rock composed of quartz, clay, and limestone, is named macigno, 

 in Tuscany; it is an argillaceous and calcariferous sandstone which, 

 from the nature of its composition being very constantly the same, de- 

 serves a very particular distinction. This rock commonly contains other 

 substances, and especially mica, which I do not consider as essential to 

 its composition. It is very abundant in the Apennines, where it charac- 

 terizes a particular formation. 



;{: I do not here cite one of the most important coal measures of conti- 

 nental Europe, that which traverses the north of France and the south 

 of the Pays Bas, because these coal measures bear so great an analogy 

 to the primordial rocks in which they are included, that I have not yet 

 entirely abandoned the idea I advanced in 1808, that these coal mea- 

 sures should also be considered as true transition rocks. 



Addition by Translator, — It is much to be regretted that the author 



