ON THE TACONIC AND CAMBRIAN SYSTEMS. 
49 
mediary groups to overlying formations, the age of which was previously well known, we 
have arrived grcidatim, and without hypothesis, at the apparently true base of the zoological 
series in Europe. It is right, therefore, that I should announce that the conventional line 
which was set up in the map of the Silurian region, between the Lower Silurian and Cam¬ 
brian rocks, and which has been adopted by Mr. Greenough, has no longer any reference 
to strata identified by distinguishing organic remains; for the same fossils are found in 
strata on each side of that demarcation. Such lines of division, however, when viewed 
as signs of local phenomena, are notwithstanding highly useful, both as indicating changes 
of lithological character, great lines of disruption, and lower divisons of the same palaeozoic 
group. In short, all researches up to this day have led to the belief that the Lower Silu¬ 
rian fossils were the earliest created forms; and that this protozoic type prevailed during 
that vast succession of time which was occupied in the accumulation of all the older slaty 
rocks, until the Upper Silurian period, when new creatures were called into existence, 
and when the earlier forms diminished, and were succeeded by a profusion of chambered 
shells which so abundantly characterize that epoch. This is, I trust, a good step gained. 
To establish upon sound data the true theory of organic succcession in the oldest forms of 
life, is surely important; and we ought to rejoice that British islands have afforded us the 
means systematically to work out the question 
It is needless to remark in this place upon the announcement of the abandonment of the 
Cambrian system. Suffice it to say that the fact is explicitly declared, and the society is 
congratulated that a step is gained in geology by the final settlement of an important 
question; and were it not for a single fact, the writer would freely acquiesce in the deci¬ 
sion, so far as British rocks are concerned. This fact is found in the existence of peculiar 
fossils on both sides of the Atlantic, which, so far as discoveries have yet been made, are 
confined to the slates of the Cambrian and Taconic system; and now the great object of 
the writer is to show that the above question has not been settled right, or according to 
facts ; or, in other words, that the Taconic rocks are not the Hudson river slates and shales 
in an altered state, or that all the Cambrian rocks are not Lower Silurian. 
§ 3. Relations and characters of the Hudson river rocks, embracing also the 
CHAMPLAIN DIVISION OF THE NEW-YORK SYSTEM. 
Before proceeding to that part of my work in which I design to describe the members of 
the Taconic system, it will be useful and proper to lay before the reader a brief view of the 
Champlain division of the New-York system, as it embraces what have been denominated 
the Hudson river rocks ; for it is by a correct knowledge of these masses, that we obtain 
the necessary facts upon which to decide the question whether we have a Taconic system or 
not. 
In 1838, in my report for that year, I stated that the Potsdam sandstone was the oldest 
sedimentary rock in Potsdam and its vicinity, and that no rock intervened between it and 
[Agricultural Report.] 7 
