Review of Recent Geological Literature. 219 
tive of structure and porphyrite is abandoned altogether. Although 
this usage is advocated by the leadingv-Ameriean petrographers, it seems 
to the reviewer to lose in precision what it gains in simplicity. 
Dr. Smith closes his dissertation with a comprehensive sketch of the 
geologic history of these islands. Along the border of the Arcadian 
trough of sedimentation volcanic outbreaks might be expected and the 
presence of ancient volcanics along the Atlantic coast has been recorded. 
Fox islands swell the list of localities for these volcanics. Pre-Niagara 
volcanic activity, giving rise to the North Haven greenstones, was fol- 
lowed by Niagara sedimentation. Subsequent to this, and even within 
Niagara time, vulcanism was again active when the porphyrites. and 
later, the acid volcanics were erupted. The history closes withi the De- 
vonian intrusion of the granitic, diabasic and dioritic m.asses. 
Six photomicrographs, illustrating excellently some typical micro- 
structures, and a geological map of Fox islands, based upon sheets 309 
and .310 of the U. S. Coast and Geodetic Sm-vey, accompany the thesis. 
This pi-esentation of the results of a painstaking investigation is emi- 
nently readable, because of its clearness and freedom from confusing 
details, and thoroughly admiraVjlein'the judicial tone of its conclusif)ns. 
F. B. 
Till fragan om fosforitlagrens upptrddande och forekomst i de geo- 
logiskaformatioiierna, af Herman Hedstrom [Geol. foren, i Stockholm 
forhandl, Bd. 18, h. 7, pp. 560-620, 8vo. 5 figs. 1896]. In this article de- 
scribing the appearance and the mode of occurrence of the phosphatic 
deposits in geological formations, we have the complement of that of J. 
Gunnar Andersson, issued a year earlier from the press of the Univer- 
sity of Upsala. This article is professedly antagonistic to the earlier 
one, and sets forth Hedstrom's views on the origin of phosphates, with 
illustration from Swedish localities. The article is divided into six 
sections which we take up in order. 
1. On a conglomerate in the lower part of the glauconite limestone of 
the Siljan\^ Silurian. [Siljan lake is in the Dal district of northern 
Sweden]. This section shows (based upon a weather surface of granite 
rock) a conglomerate bed about two feet thick with boulders of various 
elastics, and small nodules of phosphate. The rock also contains very 
sparingly distributed, examples of the brachiopod Obolus ajjollonis, 
near which the phosphate is apt to occur. Above the conglomerate is 
a thin bed (about 6 inches) of glauconite sand, supposed to be equiva- 
lent to the Ceratopyge limestone. The bed is about equally made up 
of glauconite grains and clay slate. No more than these two beds can 
be considered as Cambrian ; the rest of the section is the Orthoceras 
limestone, at the base of the Ordovician — clayey in the lower part, but 
becoming more calcareous higher up. The lower (and probably the 
middle) Cambrian is absent from this section, and the phosphate nodules 
occur in both the glauconite sand and the limestone above, as well as 
in the conglomerate at the base. Hedstrom says there are distinct evi- 
dences that the glauconite and limestone beds transgress on the Obolus 
conglomerate, and that the phosphate in them may be derived from 
