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348 [Assembly 
matter would be borne along farther, but would be deposited early ; it 
would constitute regular sandstone. Another portion would be carried 
still farther, and would probably be associated with calcareous particles. 
These would subside also, and would constitute a siliceo-calcareous 
rock. All this is in accordance with what is found in the lower rocks 
of St. Lawrence and the other northern counties. 
Near the provincial line there is a large mass of conglomerate, simi- 
lar to the millstone grit. It is 300 feet thick, and is composed entirely 
of coarse gravel and small stones. A little farther south, it becomes a 
moderately coarse sandstone ; still farther the rock is a mixture of fine 
siliceous and calcareous particles, constituting the calciferous sand rock 
of Prof. Eaton. 
From this we may learn that two rocks may be contemporaneous, 
for the deposition of the calciferous sand rock may go on simultaneous- 
ly with the Potsdam sandstone. But they will differ in two respects : 
the sandstone will be found near the shore, and of course in shallow 
water, which will be indicated by ripple marks, and it will bear, or con- 
tain those organic rehcs which are peculiar to such locations. On the 
other hand, the calciferous will be formed in deep water, and will con- 
tain the remains, generally, of those animals which inhabit deep water. 
It is evident that the lines separating two rocks found under such cir- 
cumstances, would be faintly drawn. Nature has associated them to- 
gether, and has only made a gradual transition from one to the other. 
We can find no abrupt discontinuance or commencement of either. — 
We may find gradual transitions, as in the example cited, extend to 
three or four rocks, and in the geographical range of the 2d district we 
accordingly find that it actually extends up to the Trenton limestone 
and the black slates above. In the several members constituting this 
natural association or group, there are characters in common, but a gra- 
dual departure appears, as we trace these masses upwards. 
From these remarks we may see what ought to constitute a group of 
rocks, for it is evident that a group should consist of those members, 
and those only, which were formed under the same conditions, as it re- 
gards atmospheric agency. When this agency is uniform, there will 
be a uniformity in the organic productions. The great differences will 
be produced by shoal and deep water, but the productions of one will 
pass gradually to the other. Differences will exist in the extremes, but 
