NEW-YORK TRANSITION SYSTEM. 
101 
lized that they admit of being studied in this order ; and it is an interesting fact that we com¬ 
mence on the east with the Champlain group, a little above the level of the sea; we then 
ascend up to the Ontario, and finally the Erie, which is the highest, both geologically and 
geographically. The Helderbergh rocks can only be studied in the range of highlands bear¬ 
ing that name, as they mostly disappear towards the centre of the State, though one of the 
most important members remains in full force, viz. the Helderbergh limestone. 
Another interesting fact, in connection with the great divisions of the Transition system, is, 
that the lakes which furnish respectively the names for three of the proposed groups were 
excavated out of those rocks. Thus, the valley of Lake Champlain is excavated out of the 
Champlain group ; the valley of Lake Ontario, at its southern extremity, is excavated out of 
the shales, sandstones and shaly limestones which compose the Ontario group ; and the Erie, 
out of the Ludlowville shales, shaly sandstones, etc. which also compose the Erie group. The 
Helderbergh series are well defined and limited: At the base of the Helderbergh mountain, 
an uplift, which brings into view the Champlain group, just elevates it sufficiently to conceal 
the Ontario group, so that it leans against it on the line of the upper rocks which compose 
the latter group ; as if a hand had been placed purposely to conceal all the lower rocks, and 
leave the entire mass of the Helderbergh series above, for the study of the geologist; and 
that the Avhole connection may be seen, we find the summit of this range, the Erie group, 
very well developed, the Helderbergh series lying between the Ontario and the Erie groups. 
The above remarks will give a glimpse of the value of this grouping for the purposes of 
study. In order to study the Champlain group, we go to the valley of the Champlain ; and 
it is the only valley in the State, where all the rocks composing it are found : the Ontario 
group is well developed all along the southern shore of that lake, particularly at Rochester, 
Lockport, and on the Niagara river. To study the Helderbergh series, we may cross the 
range at New-Scotland, near Clarksville, commencing our examination at the base of the 
mountain below the pentamerus limerock ; as we proceed up, we find in succession several 
well marked members of the series, all lying beneath the Helderbergh limestone, which ter¬ 
minates the series in this direction, and all of which clearly underlie the shales and shaly 
sandstones of the Erie group, which occupy the crest of the mountain. But our view of the 
Erie group is not perfect in the Helderbergh range ; and in order to see all its members, we 
must go west and southwest, or to the shore of the lake itself. It is not supposed, however, 
that its immediate shore Avill furnish a complete profile of the rocks which I would propose 
to place in this group : it will undoubtedly require many offsets from the lake, in the direction 
of the excavated valleys formed by the streams which flow into this great reservoir. 
Taking, then, a comprehensive view of the whole ground of this grouping, (for which I am 
alone responsible,) it appears to be adapted to the purpose for which it is proposed ; for, on 
examination, the student will see that the outlines of the Transition System, as well as the 
minor parts, as developed in New-York, are drawn through those planes which are termed 
neutral, and that neither group contains members which clearly belong elsewhere. It is true, 
the number of groups may be greatly increased ; but should we not be in danger of defeating 
the object aimed at in classification? It is the simplicity of the view which recommends itself 
