Reviews — Prof. Tschermak — On Volcanic Action. 569 
Two longitudinal sections along tke lines mentioned give a good 
idea of the general connexion of tke details. 
As a wkole, tke structure of tke Tyne, Wear, and Tees Coal-field 
is simple enougk, and since Buddle’s remarkakle papers on tke 
larger seams of tke district, tke general equivalence of tkese kas 
been fairly well understood. Witk tke minor seams, kowever, tkis 
is not the ease, and every one will appreciate tke Obligation under 
whick Mr. Simpson kas placed nortkern geologists and mining men 
in giving tkem the results of his observations on tke subject. In 
some instances even now tke correlation of the seams is still doubtful, 
especially in tke extreme north. Wken tkis is so, a special mark 
attacked to tke sections deuotes tke uncertainty. 
Tke nomenclature of Coal-seams kas ever been eccentric, and kere 
we kave this brought vividly before us. Tke names in use in tke 
Tyne district are not tkose of tke Wear Valley, wkile yet otker 
names are given to the same Coals in tke Derwent area. 
Tke care with wkich tkis ckart kas been drawn up is evidenced 
by the fact that even tke small seams lying between the Brockwell 
seam (tke arbitrary base of tke Coal-measures) and tke Millstone- 
grit are duly entered in tkeir places. In tkis interval we kave tke 
group of beds sometimes referred to as the Ganister series, altkougk 
the rocks composing it are indistinguiskable from tkose either above 
or below, and no marine fossils kave, so far as we are aware, been 
found in them yet. Tke fine-grained white, rootlet-pierced, sand- 
stones, wkich give tkeir name to the division, are found both in tke 
beds above the Brockwell seam and in tke Carboniferous Limestone 
or Bernician rocks far below. We are therefore pleased to see that 
Mr. Simpson includes tke series (some 300 feet tkick) in tke Coal- 
measures proper, in wkich, indeed, ke kas, very judiciously, recog- 
nized no divisions whatever. Tke entire thickness of tke Coal- 
measures, according to kirn, from the kigkest bed known in Boldon 
Colliery (between Sunderland and Newcastle), and tke top of tke 
Millstone-grit, is about 2125 feet. Wkat thickness of upper beds was 
removed before the deposition of tke Permian deposits (tke un- 
conformity of wkich is well skown in tkese sections), tkere is of 
course no means of knowing. 
Mr. Simpson’s diagram, wkile it is indispensable to all local 
inquirers, cannot fail to be appreciated by geologists and mining 
engineers everywkere as tke latest, readiest, and most accurate 
summary of all that is important respecting tke Newcastle Coal- 
field. G. A. L. 
II. — On Volcanic Aotion as a Phenomenon of the Univekse. By 
Prof. Gustav Tschermak, Member of tke Imperial Academy 
of Sciences. Read 8tk March, 1877. (From vol. lxxv. of tke 
Transactions of tke Imperial Academy of Sciences, Ist part, 
Marek number, 1877. Vienna.) 
T HE author has formerly suggested that all stars in tke course of 
their development pass tkrougk a volcanic pkase. Tke moon’s 
mountains kave been thought by Hooke, Nasmyth, and Carpenter, 
