Review of Recent Geological Literature. 121 
kaolin with the original minerals and the method of deriviation is also 
considered. w. o. c. 
Igneous Complex of Magnet Cove, Arkansas. By Henry S. Wash- 
ington. {Bull. Geol. Soc. Am., 11, 389-416.) 
This paper is an able and timely review, in the light of the mod- 
ern ideas of magmatic differentiation, of the limited and isolated area 
of plutonic rocks so carefully mapped and described to J. F. Wil- 
liams ten years ago. The scope of the paper is clearly and tersely in- 
dicated in the author's summary, from which the reviewer quotes. 
The structure of the complex is briefly described, and from the evi- 
dence of its broadly elliptical outline, relations to surrounding shales, 
the presence of an overlying zone of metamorphosed rocks, the ar- 
rangement and serial petrographical and chemical characters of the 
main types, together with other minor points, it is shown that the 
igneous complex is probably a laccolith, and certainly a unit or in- 
tegral mass of intruded magma. The component abyssal types are not 
due to successive injections as was suggested by Williams, but are 
the products of a differentation in situ of the originally homogeneous 
mass of intruded magma ("laccolithic diflferentation" of K ojn- «)■ 
The main rock types are briefly described, some new analyses being 
given ; and they are shown to form a regularly graded series, ranging 
from foyayte, through leucite-porphry, shonkinitic syenyte, normal 
ijolyte and biotite ijolyte to jacupirangyte. This serial and common 
genetic character is shown both mineralogically and chemically. It is 
probable that the dikes of tinguayte and nepheline porphyry are 
aschistic (undifferentiated injections of the stil! fluid diffeiential .^otc-s 
into the surrounding rocks), while those of the monchiquitic rocks arc 
diaschistic (products of a still farther differentiation of these zones). 
The arrangement of the abj'ssal rocks is abnormal and differs rad- 
ically from most other cases of differentiated masses, in that there is 
progressive increase in acidity toward the periphery, the analagous 
case at Umptek in Kola being especially mentioned. An explanation 
of this is based on a process of fractional crystallization or freez- 
ing of the magma, which is regarded as a solution, the solvent crystal- 
lizing first, is given; and the hj'pothesis is applied to other cases. It is 
suggested that all laccoliths and similar masses of magma may be re- 
ferred to at least four different types, dependent on the chemical com- 
position of the magma as a whole, the differences between which would 
be satisfactorily accounted for by the hypothesis. In the opinion of the 
reviewer, the explanation of this contrast between the normal centrip- 
etal acidity and the abnormal centrifugal acidity of plutonic masses 
might be strengthened and simplified by recognition of the important 
role as a solvent of water, which, so far as known, is universally pres- 
ent in magmas, and is the one important constituent which never 
freezes. w. o. c. 
A Granite-Gneiss Area in Central Connecticut. By Lewis G. West- 
gate. (Jour. Geol., 7,638-6^4.) 
This is purely a petrographic paper, describing an elliptical area 
