220° —- Letters of Mr. Brongniart, with remarks. 
It is a very important object for Geology, to ascertain the 
resemblances and differences which exist between the im- 
ressions in the different countries of the terrestrial globe. 
have been much occupied in this Jabour, and my son, who 
is devoted more particularly to botany, than to other branch- 
es of natural history, has aided me effectually in this work. 
“The bituminous formation of Westfield, near Middletown, 
appears to me very different from the formation of coal and 
anthracite of Wilkesbarre and Rhode-Island. You also re- 
‘mark that this coal (if nevertheless it be true coal) is found 
only in thin veins, that it is bituminous, &c. This forma- 
tion appears to me to have the strongest resemblance to that 
of the bituminous marl slates of the copper mines in the 
country of Mansfield and Hesse. The presence of copper 
is not an essential thing, and besides, it may be that pyrites 
or some other metallic sulphurets accompany this bitumin- 
ous formation ; what is certain and very remarkable, is, that 
this bituminous slate is perfectly similar to that of Mansfield 
and that the impression of a fish, which we find in that whic 
you have sent me, is entirely like one of the species of fish-_ 
es. found in the Mansfield slates—it is the Paleothrissum 
freislebs of Mr. Blainville—a species of fish altogeth- 
er peculiar; and which has been no where found, except 
in these formations of bituminous slates—often metalliferous, 
of the mines of Mercury of the Palatinate, and of Musse, 
near Autun, department of the Saone and Loire. Indeed 
sir, the resemblance is so striking, so complete, that if it had 
not been sent by such a person as yourself, I should have 
feared that it was a rock with the impression of a fish, which 
had been formerly transmitted from Hessia to America, for 
some cabinet, and which through inadvertency, had been 
erroneously labelled. _ 
“For the purpose of convincing you of these analogies, 
so remarkable on account of the great distance, and still, so 
complete, notwithstanding this distance, 1 send you a spe- 
cimen of the bituminous slate of Mansfield, with the impres- 
sion of.a fish, and a very imperfect, but sufficient piece of 
those from the environs of Autun. If you are desirous of a 
greater number of the former specimens, on being made ac- 
quainted with it, I will procure them for you. You per- 
celve sir, how this first and singular specimen has excited 
my curiosity, and what a pleasure you will do me if you 
