22 On the Older Red Sandstone Formation, fyc. [July, 



c. Coal measures, abundant in coal, but free from limestone. 

 E. g. in the Scotch great coal tract. 



4. A base of old red sandstone, supporting limestone, which 

 not only constitutes the foundation of the coal formation, but 

 alternates with the coal measures, often forming the immediate 

 roof of the coal seams : e. g. the Glane coal basin, described 

 above. 



5. A base of the same old red sandstone, supporting a coal 

 formation, composed, in an ascending order : 



a. Of productive coal measures alternating with beds of sand- 

 stone conglomerate. 



b. Of coal measures alternating with limestone. 

 E. g. the Sarre coal basin, described above. 



N. B. The coal measures of this basin are overlaid on the W 

 and S by the new red or saliferous sandstone ; so that if the 

 series of coal measures be continued in that direction, and 

 toward which they dip, they are withdrawn from observation. 

 Could we follow them, it appears not improbable that the suc- 

 ceeding coal measures might be found free from limestone. But 

 be this as it may, it is remarkable that in this coal field, the 

 greatest number of the coal seams are found above the funda- 

 mental red sandstone, and beneath the limestone bearing strata, 

 being thus directly connected with the former. 



The carboniferous series of all countries, whose members are 

 complete, will probably be found referable to one or other of 

 the preceding modes of association. In addition to those 

 which relate to the alternation of the carboniferous limestone 

 with the coal measures, may be cited analogous appearances in 

 Silesia and Hungary, as described by MM. von Raumer and 

 Beudant. The New Continent also presents, it seems, similar 

 relations; e. g. in the coal formation of the Ohio, in the great 

 basin of the Mississippi, where coal seams are represented as 

 occurring both above and beneath the limestone.* 



The preceding examples refer to tracts where all the members 

 of the series are present ; but in some districts, the carbonife- 

 rous limestone is found altogether wanting, the coal formation 

 being directly connected with the old red sandstone ; while in 

 others, both the limestone and old red sandstone being absent, a 

 simple coal formation is only met with. But in all cases, the 

 series, whether complete or incomplete, reposes either on tran- 

 sition, or on primary tracts, or on both of these conjointly. 



The occasional association of trappean, amygdaloidal, and 

 porphyritic rocks, both separately with the individual members, 

 and conjointly with the series in general, is now too well known 

 to require more than the simple notice of the fact. 



* See the Account of an Expedition from Pittsburg to the Rocky Mountains in 

 1819 and 1S20, by Edwin James, Botanist and Geologist to the Expedition. London, 

 1323. 



