—\ 
Reviews—Bonaventure Cherts of Gaspé. 285 
and the other 900 feet. The cherts consist of iron-stained amorphous 
silica, in which are embedded the remains of radiolaria. These 
rarely form a large proportion of the chert. The amorphous silica is 
peculiar. It is hard enough to scratch quartz and contains much less 
water than opal. In the field these cherts are interbedded with 
thin siliceous shales, but the cherts make up by far the greater bulk 
of the rock. They appear to have a striking resemblance to the 
Culm Cherts of England, and differ both in mode of occurrence and 
petrographically from flint and many other occurrences of chert. 
The Franciscan Group has been invaded by basic intrusives, which 
have metamorphosed the cherts. In some cases the alteration results 
in a quartzite, but more peculiar changes are recorded such as the 
production of spherulitic and mammillated cherts, and occasionally, 
at the contact, of glaucophane schist. 
Whilst the earlier and more descriptive parts of the paper are, 
perhaps necessarily, rather tedious, such a criticism does not apply 
to the concluding discussion of modes of origin. A comparison with 
radiolarian rocks of the West Indies shows that these cherts were not 
originally radiolarian oozes. Although the intercalation of these 
chert beds with sandstone indicates a shallow water origin, the 
author rejects the lagoon-phase theory of Dixon and Vaughan, 
largely because peculiar geological conditions are required of 
which there is no evidence, and because of the absence of calcareous 
remains. The enormous bulk of silica in these rocks is all out of 
proportion to the number of siliceous organisms present, and 
impossible to account for on the ground of precipitation from 
ordinary sea or river water. The general indications of igneous 
activity makes the author’s supposition reasonable that submarine 
siliceous springs largely contributed the supply. It is further 
considered that this silica was precipitated together with 
terrigenous material, and that the rhythmic alternation was due 
to the segregation of the silica from the colloidal mass. The 
rhythmic bedding differs rather from the precipitation banding of 
Liesegang, on account of the continuous concentration of closely 
spaced bands, and also in the presence of transgressive bedding. 
This hypothesis i is studied in a set of ingenious experiments on the 
rhythmic separation of a silica gel from intimate admixture with 
mud, and these deserve the close attention of all workers interested 
in segregation probleins. 
W.. A. R. 
THe ForRAMINIFERA OF THE BONAVENTURE CHERTS oF CasPf, 
By R. M. Baee. Bull. N. York State Mus., Nos. 219, 220. 
Fifteenth Report of the Director, 1918. &vo., 60 pp., 6 plates. 
Albany, 1921. | 
HE careful examination of six thin rock sections of chert pebbles 
from the Bonaventure’ formation (Devono- Carboniferous) 
of the Gaspé Peninsula, Canada, by Dr. R. M. Bagg, has given 
