Geology and Mineralogy. 349 
It is to be followed by one dealing with the well known “ rhombic 
porphyries.” 
The rocks now under discussion occur in dikes and are fine- 
grained and porphyritic. They consist essentially of alkali-feld- 
spars and egirite; where the silica percentage is high, quartz is 
also developed (grorudite) ; with falling silica it disappears (sélvs- 
bergite) and below 60 per cent nephelite comes in as an important 
constituent (tinguaite). A fourth member of the series would be 
a rock with silica below 50 per cent and with nephelite preponder- 
ating over feldspar. This type the author recognizes in a rock 
described by Kemp* from Beemersville, N. J. and proposes for 
it the name of sussexite. This name, however, is clearly objec- 
tionable, if indeed it be not entirely ruled out by the fact that it 
has been applied since 1868 to a well-defined mineral species 
occurring at Franklin Furnace, N. J. 
These rock types are described as to their occurrence in the 
fieldand mapped. Their petrology is discussed in detail and is 
accompanied by many analyses, plates, drawings and tables of 
mineral contents. Incidentally the author takes occasion to dis- 
cuss and classify the alkali-iron hornblendes, introducing a new 
member to which the name of kataforite is given. His classifica- 
tion is as follows: 
Barkevikite angle ¢~c small TiO, rich ruling brown pleochroism 
12°-14° absorption colors ¢>b>a 
Kataforite angle cac large TiO. poor ruling red 
30°-60° absorptions b>c>a 
Arfuedsonite angle c~cvery large TiO.free ruling greenish 
Riebeckite ? 75-86 blue colors a>b>c. 
A large portion of the book is devoted to theoretical petrology, 
and it is this that will be read with the greatest interest. Many 
new and important questions are brought up and discussed and 
much light is thrown upon old ones. In the brief limits of this 
notice it is impossible to do more than merely mention this fact, 
but it may be safely said that the importance of the present 
work in its bearing on general petrology can hardly be over- 
estimated. En. Va, Bs 
9. Directions for collecting rock specimens.—A useful series of 
papers, giving specific directions for collecting specimens in the 
field and preparing them for safe shipment, has been prepared by 
the Smithsonian Institution. Sufficient illustrations are given to 
guide the untrained in the preparation of tools and in methods of 
manipulation. The articles are entitled as follows: “Directions 
for collecting rocks and for the preparation of thin sections,” by 
Grorce P. Merritt, 15 pp.; “ Directions for collecting and pre- 
paring fossils,” by CaarLes ScHUCHERT, 31 pp.; “ Directions for 
collecting specimens and information illustrating the aboriginal 
uses of plants,’ by Freprrick V. Covii1s, 8 pp., and “ Direc- 
tions for collecting minerals,” by Wier Tassiy, 6 pp. (Bull. 
U.S. Nat. Mus., No. 39, Washington, 1895.) 
* Trans. N. Y. Acad. Sci., vol. ii, p. 60, 1892. 
