THE NAMING OF ROCKS 695 
the world over. However numerous the names for the sedi- 
mentary rocks may be in the future, the method still must be 
used, for however fine the discriminations resulting from such 
names, there will be variations from the meanings assigned to 
these names, and thus the local names are necessary. 
Ln exceptional cases plan followed with igneous rocks.—The sim- 
ple method proposed of designating the slightly different varie- 
ties of igneous rocks from one another, without throwing their 
nomenclature into hopeless confusion, has already been followed 
in several cases. 
A notable instance is the term Andendiorite proposed by 
Stelzner* for a particular rock which has the general characters of 
a diorite, but which in some respects differs from ordinary diorite, 
and occurs in the Andes. A geologist who does not care to go 
into the detailed petrography of the region notes at once that in 
the Andes is a rock which has the general characters of the dio- 
rites, but which in some respects differs from the ordinary kind. 
He also at once knows that in the Andes is a rock which is dif- 
ferent from the ordinary diorites, but which is allied to them. 
If in his investigative work he wishes to know exactly the 
meaning of the modifying term, he can do so by reading Stelz- 
ner’s paper, or by obtaining specimens and an analysis of the 
rock. Inthe case of Andendiorite, the name has been also used 
as a new specific name, an dapplied by Iwasaki? to a somewhat 
similar rock in Japan. Toa certain degree this shows how the 
method may be made to work out in practice in reference to the 
igneous rocks. When here and there other rocks are discovered 
similar or almost identical with the Andendiorite, and this variety 
of rock, asa result of these investigations, is found to be so 
abundant and so definite in its characters as to demand a specific 
name, the original word Andendiorite may be used for this pur- 
pose, or, better, a new specific name may be coined for it, and 
the rock be placed in the scheme of rock nomenclature. 
Rosenbusch has used the method of geographical qualifiers 
* A. STELZNER: Geologie und Palaontologie, von Argentina, p. 213. 
? Andendiorite in Japan, by C. IWASAKI: JouR. GEOL., Vol. V. 1897, pp. 821-824. 
