694 C.. R. VAN HISE 
not followed it. Was there not some good reason for the intro- 
duction during the past years of many new, independent names ? 
The answer is, petrographers had not worked out any plan as to 
the naming of rocks, and to assign a new name for each new 
variety of rock was the easiest way out of the difficulty, although 
it was disastrous so far as their fellow workers were concerned. 
Then the honor of giving a new name to rock nomenclature 
doubtless had a too important effect. Furthermore, many of 
the petrographers still held, in a subconscious way, to the old 
notion of rock types, not yet having grasped the idea of general 
gradation. 
Plan followed in case of sedimentary rocks—That the scheme 
proposed is practicable is shown by the sedimentary rocks, where 
it has been substantially followed, although as a matter of neces- 
sity rather than a conscious system. In the sedimentary rocks, 
from the first, gradations were recognized, and hence the tend- 
ency to give each variety a new name never got any headway. 
To illustrate the application of the scheme to the sedimentary 
rocks, we may take the sandstones. There is an almost infinite 
variety of sandstones, but it so happens that petrographers have 
not been directing their energies to the minute discriminations 
of their variations, and we have nota dozen or score of different 
names for the different kinds of sandstone. Yet the sandstones 
of different localities are discriminated and recognized as dif- 
ferent from one another by attaching the names of the localities at 
which the rocks occur to the name, and thus discriminating each 
rock from all others. For instance, in Wisconsin a peculiar sand- 
stone occurring locally is called the Madison sandstone. From 
this designation the general geologist at once knows that this 
formation has the general characters of the rocks which have 
been called sandstone, and he will not go further. But if he is 
interested in the Madison district for some reason, scientific, 
economic, or otherwise, he may go further and learn the pecul- 
larities of the particular sandstone which is found at Madi- 
son. 
By this method the sedimentary formations are discriminated | 
