THE NAMING OB ROCKS 
Introduction of new names.—tIn the early days of petrography 
it was supposed that there existed rock types as definite as ntin- 
eral types. Following this hypothesis, a rock found which was 
different from any rock before described was immediately given 
anew name. This went so far that an altered rock was given a 
family name, as in the case of diabase, an altered dolerite. After 
some years a scheme of nomenclature was worked out which was 
supposed to be approximately complete. For a time subse- 
quently, when a rock was discovered having a somewhat different 
character from previously known rocks, it was referred with 
modifying mineralogical prefixes to some of the so-called types. 
A few years ago another period of name-giving was inaugu- 
rated. During this period, which continues to the present time, 
petrographers have introduced numerous new, independent 
names, both for long-known and for newly-discovered varieties 
of rocks. Since 1890 more than fifty new names have been 
added to the nomenclature of the igneous rocks, a larger number 
than young petrographers were obliged to know the meaning of 
before 1890. The stage through which petrography is passing 
is somewhat similar to that through which at one time paleon- 
tology passed. One might almost think that petrographers were 
seeking to find varieties of rock slightly different from those 
before known in order to give them new names. 
Method in giving new names——The method of petrographers 
in proposing names, so far as any method is discoverable, is to 
give an independent name to each rock which is slightly differ- 
ent from any previous rock found, without reference to any defi- 
nite plan of nomenclature. The greater number of the names 
are not proposed to designate varieties which are subordinate to 
previously recognized kinds of rocks, but are names coérdinate 
with those before used. In petrography, a binomial nomencla- 
ture thus far has not been generally adopted, and therefore it has 
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