Geological Systems — Geological Maps, ^rc. 255 



pleasure to see our young geologists so far on the right road. 

 They have proved that they are fit to walk alone, and to make 

 the best use of their senses. It is probable they may be forc- 

 ed to make a system for each of the valleys or basins filled 

 with alluvial or secondary, and after that, it appears to me 

 doubtful, whether any one of them will apply either to our 

 immense alluvial on the shores of the Atlantic, or to our ex- 

 tensive secondary of the basin of the Mississippi. 



Extracts of a letter to the Editor from William Maehre, Esq, 

 dated, Paris, January 10, 1825. 



GEOLOGICAL MAPS OF PORTIONS OF CONTINENTAL 

 EUROPE. 



" Even at this time, there is no geological map of a whole 

 country on the continent of Europe, and the maps of all the 

 partial basins and patches of mountains yet published, would 

 scarcely cover the surface of the state of New-York or Penn- 

 sylvania. 



A critic in the Bulletin des Sciences considers me as in- 

 accurate, because I have not found coal under chalk, lime- 

 stone, or the old red sand-stone. The impression that coal 

 may be thus found, originated, as I suppose, from Smith's 

 map of England. This author takes it for granted, because 

 the primitive rocks emerge on the west side of the island, that 

 all the secondary of the east lies upon the secondary of the 

 west, and consequently that the chalk and limestone of the 

 east repose upon the coal and coal measures of the west, 

 agreeably to the section which he gives of the island. This 

 is contrary to the observations I have been able to make, 

 all of which tend to convince me, that secondary basins do 

 not overlie one another, but touch only at their borders and 

 sides — a different order of stratification occurring in each, 

 agreeably to the nature of the surrounding heights, with the 

 particles proceeding from whose decomposition the basins 

 were originally filled. 



I have still my doubts, notwithstanding what the critic has 

 said, whether the argillaceous oxide of iron ; so common in 

 coal mines, is a carbonate of iron. I have also my doubts, 

 whether the chalk forms a good foundation for what is called 

 the tertiary class of rocks, of which class 1 am unfortunately 



