Geology of the Lake Superior Land District. 13 
one hand, the New York and Canadian geologists have traced the 
Silurian groups up to the eastern borders of our district ; on the 
ents, or to subdivide them according to the paleontological 
evidence, 
Under these circumstances, we have endeavored to connect the 
two sets of observations and blend them into one harmonious 
whole. As the New York survey is the only instance in which 
nomenclature, so far as the same groups described by the New 
York geologists could be recognized in our district. 
. The designation of groups of strata by names derived from 
their geographical position, or from the locality in which the rocks 
are first investigated and their relative position clearly defined, 
_ Seems to be of all the methods of nomenclature that which, for 
the present at least, is liable to the least objection. Names given | 
solely with reference to lithological character, or to the presumed 
predominance at any particular point of a certain genus or class of 
organic remains, seem much more likely to lead to misunderstand- 
ing and confusion ; and, however desirable it may be that a uni- 
versal system of nomenclature and arrangement should be in- 
troduced, it seems quite impossible to hope for any such thing in 
the present state of geological science, a science which is so rapidly 
developing, and liable to such constant changes. ‘The names in- 
troduced by the New York geologists, are in most instances de- 
tived from the locality where the group designated is particularly 
well developed, and the fact that those groups have, in their con- 
Unuation through Canada, been described by Mr. Logan, the Pro- 
vincial geologist, under the names recognized by the New York 
survey, seems an additional reason for their adoption, as far as 
possible, by us. 
It will be seen from the details incorporated in a subsequent 
part of this report, that many members of the Silurian series, par- 
ticularly the grits and conglomerates, which are clearly defined 
1n New York, have but a limited range, and disappear altogether 
before reaching the limits of our district. These are conditions 
Which we ought to expect would exist in deposits made along a 
shelving ocean-shore ; but so far as these are persistent, it seems 
desirable that they should bear the same names throughout their 
Whole extent, 
