1881 .] 
253 
[Wadsworth. 
Granite. 
Looking next at the granites it is to be seen that in 1870 (Vol. 
Ill, pp. 1-9), all the granite in the district (at least all between the 
Sierra Nevada and the eastern side of the Wahsatch range) cov- 
ered by the Fortieth Parallel Survey was regarded as eruptive, 
and of late Jurassic age. It was promised that reasons for this 
view would be fully given in Yolume I. It was also stated that 
the last of the publications would be issued in 1871. From this, 
as well as from other data, it is to be understood that the field 
work had ended prior to the publication of Yolume III (1870). 
In 1876 Yolume YI, by Professor Zirkel, was issued. The 
arrangement of the granites was found to be changed in this, but 
no reason for the change, nor any mention of the former view 
was given. In this the granites were held to be thus classed : 
(Yol. YI, pp. 39, 40, 58, 59.) 
I. Metamorphic granites. 
II. Older eruptive granites of ante- Jurassic age. 
III. Younger eruptive granites of Jurassic age. 
It was again stated : “ The full details of the reasons of this 
assignment will be found in the chapter upon granites in Y ol. I of 
this series.” (YI, p. 39.) It was further remarked that “ Clarence 
King has long since shown that the eruptive Jurassic granites, and 
only these, are characterized by the presence of macroscopical 
titanite.” Where ? Professor Zirkel also shows by the following 
remark that his classification of the granites was derived from 
the work on this collection alone, and not from his previous stud- 
ies : “It should be particularly stated that the described contrasts 
are valid only for the examined rocks of the Fortieth Parallel, 
and that it is not allowable to generalize from them for other 
countries ” (YI, p. 59). Since there is no a priori method whereby 
eruptive granites can be distinguished from supposed metamor- 
phic ones microscopically, and Professor Zirkel had not studied 
them in the field, the classification must have come originally 
from Mr. King and his assistants. 
Turning now to Yol. I, published in 1878, it is to be seen that 
Mr. King divides the eruptive granites alone into four types, 
remarking, “ This classification, based upon field observations, 
