No. 380.] REVIEWS OF RECENT LITERATURE. 615 
to eight inches. Their nuclei are usually lighter in color than their 
peripheral portions, and contain often little bunches of tourmaline 
and plates of muscovite. In some places the nodules are arranged 
in rows. Sometimes the nodules of a row coalesce and pass into a 
continuous band with all the properties of a vein. Through the 
veins are scattered bunches of tourmaline, like those in the centers of 
the nodules ; and the central portion of the vein, like the nuclei of 
the nodules, is composed of feldspar and muscovite. Its periphery, 
like the peripheries of the nodules, consists principally of quartz and 
sillimanite. Analyses of the granite (I) and the nodules (II) show 
the latter to be the more siliceous and the less alkaline. 
SiO, ALO, FeO, CaO MgO K.O: NaO Loss Total 
I 7883 10.88 1.63 ae 35 5-31 2.13 .32= 99.67 
II 81.43 13.70 1.58 =37 06 1.28 1.02 -92 = 100.36 
From a consideration of the manner of occurrences of the nodules 
and their composition when compared with the granite, Adams con- 
cludes that they were derived from the crystallization of a magma 
which was free to gather itself into rounded drop-like forms which 
the isolated portions of such aliquid would take, but which could 
not be developed in a magma when crystallization was far advanced. 
The rock of the Great Whin Sill in Durham and Northumberland 
has profoundly altered the carboniferous limestones, shales, and 
sandstones with which it is in contact. Hutchings! declares that 
the pure limestones have simply suffered crystallization except in the 
immediate contact with the eruptive where garnets have sometimes 
been produced. The eruptive, on the other hand, has had developed 
in it both small garnets and small flakes of a brown biotite. Argilla- 
ceous limestones have suffered a great deal more change than the 
purer limestones. The new contact minerals found in them are garnet, 
augite, idocrase, wollastonite, epidote, hornblende, feldspar, chlorite, 
and sphene. The shales have become indurated. Chlorite and 
muscovite have been formed in large quantity and “ spots” have de- 
veloped. In many of the shales, especially sandy varieties, much 
of the quartz has recrystallized, feldspar has been produced, and the 
characteristic contact minerals, andalusite, biotite, anthophyllite, etc., 
have originated. The calcareous shales are the most intensely altered 
of all the beds in the district. They yield a hornfels filled with garnets, 
idocrase, spinel, wollastonite, and, in short, all the other minerals 
Characteristic of the altered argillaceous limestones and the shales. 
1 Geol. Magazine, vol. v, pp. 69, 123, 1898- 
