676 H, S. WIELIAMS 
the geological systems is both practicable and necessary to the 
true representation of the facts in the case. 
It is this fundamental characteristic of the United States 
scheme which furnishes the answer to the question quoted at 
the beginning of this article from the “Symposium” of a few 
months ago, The system which should be adopted provisionally 
for current use, both by geological workers and by teachers, 
must recognize this fundamental fact, that the units which it is 
attempted to name and classify in stratigraphical geology, are 
not constant units, presenting uniform characters for the whole 
world or for each continent, but are very inconstant, preserving 
the same characters for only very limited areas. 
Since this is known to be the actual fact regarding geological 
formation, it is useless to attempt to hold to a rigid system of 
nomenclature, or to raise the vain hope that the use of the same 
names will help us over the difficulties arising from the great 
diversity of facts. 
Having recently attended the meeting of the International 
‘* Commission des classifications stratigraphiques’’ in Berlin, it is with 
great pleasure that I am able to report that the commission 
appointed at the St. Petersburg Congress adopts this principle 
of elasticity in all matters of detail as a foundation principle in 
the construction of rules for use in discussing international strat- 
graphy. Professor Renevier, the chairman of the commission, 
has not yet published his official report of the proceedings, 
hence I will not attempt the discussion of details until the report 
is received. But I believe it will interest all American geolo- 
gists to know, that several principles, which we believe in, and 
on account of which has arisen some of our dissatisfaction with 
the European nomenclature and classification adopted by the 
International Congress for the map of Europe, will be recom- 
mended as the basis of an international system of classification. 
One of these points is the recognition that the so-called 
systems, or units of the second order, are the smallest divisions 
of the geological scale to which uniform names and position in 
the classification can be given in an international scheme. 
