1895,] Petrography. 155 
Rutley’ gives a few illustrations in proof of his statement that the 
production of spherulites is sometimes a devitrification process subse- 
quent in point of time to the development of perlitic cracks in the 
volcanic rocks in which they occur. 
In a recent number of Science Blake’ suggests the notion that many 
of the quartz veins, ‘ reefs’ and boss-like masses in ancient rocks are 
the result of deposition from old thermal springs. 
The rock of Saint Sardoux, Puy-de-Dame, France, is composed’ of 
ilmenite and soda-augite in a groundmass consisting largely of nephe- 
line crystals cemented by a matrix of feldspar and glass. Sometimes 
the augite and nepheline are intergrown like the constituents of a peg- 
matite and at other times they form an ophitic aggregate, with the — 
nepheline the older component. The rock penetrates the peperites of 
the region in the form of dykes and veins. 
New Books.—Granites and Greenstones” is the title of a new series 
of tables for the determination of rocks and their essential components. 
The author, Mr. Rutley, divides rocks into Volcanic rocks, Dykes and 
Sills and Plutonic masses, and then subdivides each group into four series 
as follows: Ultra-basic with SiO,-—-39-45 per cent; basic, with silica 
45-55 per cent, intermediate, with SiO,—-55-66 per cent; and acid, 
with silica over 66 per cent. The ultra-basic series is divided into the 
non-feldspathic and the potentially feldspathic, including nepheline 
and leucite non-feldspathic rocks. The basic rocks are all plagioclastic. 
They include a nephelinic or leucitic and a non-nephelinie group. In 
the dyke and sill division of this series are included the diabases. In 
the intermediate series we find again two groups—the orthoclastic and 
the plagioclastic, and in each of these nepheline and non-nepheline 
sub-groups. The acid series includes a division whose feldspars are 
plagioclase or anorthoclase, and one in which the feldspar is orthoclase. 
Definitions and notes are abundant and are so given as to really 
explain the tables. The elvans are described as the apophyses of 
deep seated granitic masses. They include micro-granites, aplites, 
quartz-porphyries and greisens. The mineralogy tables contain no 
startling novelties. They are good and the book itself is well worth 
study. It will serve as a useful companion to the student. 
7 Quart. Jour. Geol. Soc., Feb. 1894, p. 10. 
ê Science, Vol. xxiii, 1894, p. 141. 
° Bull. Soc. Franc. d. Min. xvii, p. 43. 
10 Granites and Greenstones, a series of Tables and Notes for Students of Pet- 
rology. By Frank Rutley. London, Thos. Murby, 1894, pp. 48. 
