420 The American Naturalist. [May, 
Lamprophyres near the Shap Granite Mass.—-Near the Shap 
granite in the North of England there are numerous dykes of minette 
and kersantite that are believed by Harker’ to be the dyke facies of the 
granite, just as fourchite and ouachitite are regarded by Rosenbusch 
as dyke facies of eleolite-syenite. These lamprophyres_ contain many 
rounded blebs of quartz and corroded crystals of orthoclase, both of 
which appear to owe their present shapes tu resorption processes, since 
both minerals are surrounded by resorption borders. The dyke rocksare 
thought to be genetically connected with the granite because of their 
age and distribution, and because of the fact that they contain the 
quartz and orthoclase above referred to, and also sphene, which is a 
characteristic component of the granite. A study of the literature of 
the lamprophyres shows that these rocks are often associated with — 
granites, and hence Harker believes that the group may be discovered 
to be genetically related to this group of plutonie rocks. A $] 
feature of the lamprophyres pointed out by the author is that while the 
total alkalies in them is about equal in amount to the sum of the alka- 
lies in the associated granite, the potash in the former always bears# 
larger ratio to the soda than it does in the latter rock. It issu 
that the granite and the lamprophyres are portions of the same magma 
that became differentiated by gravity. From the supernatant layer, 
which was acid, quartz and orthoclase separated and then settled down 
into the lower basic portions of the mass. These were then partially 
dissolved, the solution of the orthoclase accounting for the large pr% 
portion of potash in the lamprophyres. In a later paper the 
argues against the view of Diller and Iddings that the sporadic quartzes 
in certain basalts and other basic rocks are the result of ¢ a 
tion under other than the normal conditions. He thinks that in all 
these cases the quartz may have originated as outlined above. 
The Geology of Conanicut Island, R. I.—The carboniferous 
Phyllites of Conanicut Island in Narragansett Bay are cut by “a 
of coarse-grained muscovite granite porphyry that has produced € 
effects in the surrounding sedmentaries.» The granite, whl a 
many evidences of its intrusive nature, was regarded by bedded 4 
metamorposed clastic rock, forming the lowest member of the 
series at this place. The phyllites near the contact with the granite ] 
* Geol. Magazine, 1892, IX, p. 199. 
*Ib. IX, p. 485. 
= V. Pirsson. Amer. Jour. Sci., 1893, XLVI, p. 363. 
Proc. Bos. Soc. Nat. Hist., 1883, XXII, p. 179. 
ch exhibits 
