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Geologieal Systems—Geological Maps, Gc. 255 
aye to see our young geologists so far on the right road. 
hey have proved that they are fit to walk alone, and to make 
the best use of their senses. It is probable they may be fore- 
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 hear of the Mississippi. 
is — pet 
Exiracts Ga: a spe to the Editor from William Maclure Esq. 
ated, Paris, January 10, 1825 
GEOLOGICAL MAPS OF Pil hh OF CONTINENTAL 
gene Evin at this time, there is no geolo ical map of a whole 
country on the continent of Europe, local maps of all tke 
partial basins and patches of mountains yet published, would 
ees. 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 c 
may be thus found, originated, as I suppose, from Smith’s 
map of England. This author takes it ioe 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 _— which he gives of the island. This 
is contrary to the observations I have been able 
all of which sand: to convince ae that seconda 
not overlie one another, but touch only at their 
sides—a different order of stratification occurring in 
agreeably ¥ the nature of the surrounding heights, with the 
lic oceeding from whose decomposition the basins 
were ivigionly fille 
have still my doubts, notwithstanding what the critic has 
said, whether the argillaceous oxide of iron; so common in 
coal mines, isa carbonate of iron. I have also my doubts, 
whether the chalk forms a good apa for what is called 
the tertiary class of rocks, of which class ] am unfortunately 
