No. 380.] REVIEWS OF RECENT LITERATURE. II 
roughly by variety of color into three horizons, or rather bodies, as 
their shape is irregular, in each of which diamonds are said to have 
been found. A careful consideration of the materials of these vari- 
ous clays leads the author to consider that they represent an origi- 
nal group of phyllites of varied character, but chiefly of clastic origin, 
threaded with veins of pegmatite, and possibly containing some 
eruptive material of more basic character. Assuming the correctness 
of this analysis of this very obscure and difficult problem of “ mud- 
geology,” it becomes desirable to know, first, whether the pegmatite 
was eruptive and may have exercised a metamorphic action upon the 
schists, or was secretionary ; second, whether the diamond belongs 
to the pegmatite or to the country rock. The first question the 
writer decides in favor of the eruptive hypothesis, although the evi- 
dence is not conclusive. The second he considers it necessary to 
leave an open one, but the indications seem to favor the view that 
the diamonds were formed in the phyllites on the border of the peg- 
matites and presumptively through the agency of their eruptive 
action, the phyllites having provided the carbon which is shown to 
be amply sufficient. 
Etching Figures of Triclinic Minerals. The writer has investi- 
gated several triclinic minerals by the etching method for the purpose 
of determining whether they possessed the holohedral centro-sym- 
metry of that system. His experiments on tourmaline (hexagonal, 
hemimorphic) and on cleavage plates of acid dextro-tartrate of stron- 
tium (triclinic, hemihedral) showed that the etching figures produced 
on two parallel crystal faces of unlike physical character were dis- 
tinctly different, sufficiently so to be used as a safe means of deter- 
mining such unlikeness. The tests recorded were made upon the 
following minerals, the result in all cases being confirmatory of their 
accepted holohedral character : axinite, cyanite, copper sulphate (arti- 
ficial crystals), rhodonite, albite. On the tourmaline and cyanite the 
etching was produced by the action of a fusing mixture of acid potas- 
sium sulphate and fluorite, on the others by a mixture of equal por- 
tions of sulphuric and hydrofluoric acids. The results add to our 
knowledge of the etching figures of some of the minerals named, 
although negative as far as concerns the point investigated. 
Clinohedrite, a New Mineral from Franklin, N. J.2— The new 
mineral was first found by Mr. Nason some two years ago, but more 
1 Walker, T. L. Amer. Journ. of Sci., vol. v, p. 176, 1898. 
2 Penfield, S. L., and Foote, H. W. Amer. Journ. of Sci. vol. clv, p. 289, 1898. 
