114 Remarks on the Ancient Flora of the Earth. 



transition rocks and the coal Jbrmation ; the second is confined 

 to the formation of the variegated sandstone, the third con- 

 tains all the strata of keuper, to the lowest members of the chalk 

 formation, and the fourth comprehends all the formations found 

 above the chalk. Though the details given by M. Brongniart 

 seem so far to favour this distribution, we cannot help remarking, 

 that it cannot be adopted in a purely geognostical sense, and that 

 We, at first sight at least, can recognise only the first and last 

 periods as independent formations. The author himself, indeed, 

 makes the same remark, when be states that the second and 

 third of these different periods do not very closely correspond 

 with the divisions which the most of geologists receive as sepa- 

 rate groups of formations. It appears to us, also, as if he had 

 not sufficiently considered that the distinctions adopted by him- 

 self are founded only on the local relations of the rock forma- 

 tions, and cannot consequently possess a general character. We 

 cannot, indeed, with propriety, consider the separation of the 

 first and second periods by the formations of the old red sand- 

 stone and the magneslan limestone or zeclistein as by any 

 means generally prevalent ; for it is at present universally ac- 

 knowledged, that though, in a great part of Germany and Eng- 

 land, such a separation may take place, either in both formations, 

 or in one of them, nevertheless, in other extensive districts, no 

 difference can be pointed out between old red sandstone, and 

 the superimposed new red sandstone. We are hence obliged to 

 consider both rock formations as nothing else than the under 

 and upper strata of one and the same formation in which 

 the formation of magnesian limestone or zechstein but occa- 

 sionally makes its appearance as a subordinate bed, and that 

 always of small extent. Our author cannot possibly be igno- 

 rant that this view is very strikingly exemplified in the rocks 

 of France. In no part of that country has a bed of hniei 

 stone been found, which could, with any probabiHty, be com- 

 pared with the magnesian limestone or zechstein. This is also 

 known to be the case in the south of Germany, and, as far as our 

 observation extends, among the Alps also, where, nevertheless, 

 the conjunction of red sandstone with quartz porphyry is known 

 to be nothing uncommon. In the northern parts of the British 

 islands, in which strata so like copper-slate or kupferschiefer 



