190 
[Assembly 
logical antiquity of all our great horizontal western region than 
had been given to it. This opinion was communicated to Profes- 
sor Cleaveland, and was published in the American Journal of Sci- 
ence and Arts for 1829. Since then, all other information collect- 
ed of the parts examined, has only tended to strengthen my con- 
viction of their transition character. 
In the rocks of -the fourth district we have all those fossils which 
in Europe are characteristic of the transition class: these are ortho- 
cera, trilobites, producti, spirifers, peniameri, and favosites, and on 
the authority of Mr. Conrad, eurypterus, catenipora, conularia and 
monotis. 
In a report like the present one, it would be altogether prema- 
ture, and wholly at variance with the wisdom displayed in the ar- 
rangement of the survey, to attempt any geological arrangement 
of the different masses or subdivisions to be spoken of, whatever 
might be the information possessed or opinion entertained, unless 
where practical information is to be given; wisely considering from 
the nature of the annual reports, restricted as they are to objects 
of immediate utility, that all such information should be reserved 
for the final report, when the matured results of the whole period 
allotted to each one in his district, and of the whole number enga- 
ged in the survey, shall be obtained. So likewise we omit all au- 
thorities as to localities, giving those only of minerals and fossils 
which have come under our observation, not however as new — to 
the contrary not doubting that all are on record; believing that all 
historical information of the kind should be reserved to the final 
publication. 
Sandstone and shale, as we said, form the predominant masses 
of the fourth district, eleven of the fifteen counties having no other 
kind of rocks, from their most elevated surface to the lowest ex- 
cavation which exists. With exceptions inconsiderable as to num- 
ber and extent, great uniformity exists between the sandstone and 
shale, from their alternating, intermixing, and usually accompan}'^- 
ing each other; from their having the same disposition in layers 
and beds, the same horizontal position, and usually of the same 
thickness, colors, fossils, and mineral contents. 
The prevailing color when recently broken, is some shade of 
green, which, by long exposure to the air, often assumes a brown- 
ish hue. This effect is owing to manganese, which seems to be 
