JUNE 18, 1884.] 
portion of the work is more difficult to follow, 
owing to the necessity of subdividing the cross- 
sections, like the previous parts of the book, in 
accordance with the limits of the great forma- 
tions. This difficulty is inherent in the case, 
and lies in deciding how to put the diverse 
phenomena before the mind in ‘ natural order’ 
(much-abused phrase). If we follow the geo- 
graphical divisions, there must be a continual 
interruption and resumption of the same geo- 
logical horizon; whereas, if the geological 
boundaries are alone regarded, the geographical 
continuity is broken. Of the two solutions, per- 
haps the second is the better. The first of these 
subdivisions (chap. i.) is the ‘ primitive ter- 
rane’ (used by de Castro to imply nearly what 
is meant by the archaean of Dana). It is very 
interesting in this connection (and not unex- 
pected), to find that the upper division of the 
‘ primitive’ consists of the roches vertes which 
occupy this position in South Wales, the Ap- 
palachian belt, and in so many: other places. 
They are mingled with chlorite schists and talc 
schists overlying the mica schists of Villalba, 
which latter contain biotite, muscovite, orthose, 
plagioclase, and two kinds of quartz; with 
garnet, zircon, sphene, and oligiste as acces- 
sories. Gneiss has been observed by Dr. 
Barrois only in subordinate thin layers inter- 
calated among the mica schists. 
The same is true of the garnetiferous am- 
phibolites; but the difference between this 
Spanish stratigraphy, and that of those regions 
where similar rocks have been observed in 
America and in Europe, is, that the series in the 
former case are concordant. ‘The Laurentian 
would appear, from Dr. Barrois’ conclusions, to 
be wanting in the outcrops of Galicia, and the 
above-mentioned measures to represent a great 
development of the Huronian. The succession 
of Cambrian beds, both in the Asturias and in 
Galicia, he finds perfectly in accordance with 
Barrande’s views of this part of Europe. From 
a fossil of Archaeocyathus (Billings), character- 
istic of the Potsdam sandstone, found in the 
limestones of El] Pedroso, MacPherson forms a 
column in which he thinks that possibly the 
Laurentian is represented at the base by mica 
and tale schists, with intercalated limestones of 
various colors, and sometimes filled with acti- 
note (actinolite), and, more rarely, intercalated 
beds of felspathic grauwacke. On this rest 
argillaceous, splendent, siliceous talc schists, 
sometimes containing chiastolite; and on these, 
three benches of conglomerates, tuffs, and ar- 
gillaceous schists and limestones, which he re- 
fers to the Potsdam sandstones. 
Following this are details of the sections in 
SCIENCE. 129 
the Devonian and carboniferous. ‘The sixth 
chapter treats of the phenomena which have 
modified the position of the paleozoic strata 
since these latter have been deposited. His 
conclusion is, that the Cantabrian Mountains 
owe their origin to two distinct lines of press- 
ure; the one acting along east and west, and 
the other along north and south, lines. The 
former occurred between the carboniferous and 
Permian ages; and the latter, between the 
eocene and miocene. 
The last subjects treated are the effects of 
denudation and the details of the actual surface- 
relief. 
The work has been built on strong and sure 
foundations, and will long be cited as an au- 
thority. It is full of new facts and suggested 
analogies, and is characterized by thoughtful- 
ness, industry, and modesty. 
LOCKWOOD’S ELECTRICITY. 
Electricity, magnetism, and electric telegraphy : a prac- 
tical guide and handbook of general information for 
electrical students, operators, and inspectors. By 
Tuomas D. Locxwoop. New York, Van Nos- 
trand, 1883. 377 p., illustr. 8°. 
As indicated in its preface, Mr. Lockwood’s 
unpretending book is not primarily intended 
for those having any considerable previous 
knowledge of the subject of electricity, but 
for the large number of persons who have not 
had the advantage of a scientific education, 
and yet find themselves in the employment of 
telegraph, telephone, or electric-light com- 
panies in various subordinate positions. To 
this class of persons the information contained 
in the work will doubtless be of great value ; 
and, indeed, we do not recall any one book, of 
moderate size and price, in which so many 
of the different applications of electricity are 
considered in an elementary manner. ‘l’o one 
familiar with the subject, the treatment of the 
more important topics must, of course, seem 
brief and occasionally superficial ; but, recol- 
lecting the design of the work, it can hardly 
fail to win commendation, even from those who 
most clearly recognize its deficiencies. 
The chapters on line-construction, office ar- 
rangements, and the adjustment and care of 
instruments, are excellent: and a very clear 
description of the principles of duplex and 
quadruplex telegraphy is given. ‘There is also 
a good account of Mr. Gray’s interesting 
harmonic multiple telegraph. Mr. Delany’s 
ingenious multiplex synchronous telegraph is 
not described, probably because it did not 
