26 
Challenger some years ago this minute structure was looked 
upon as what is known to petrographers by the name of 
“fluxion-structure,”” such as may be seen in obsidian and 
other volcanic rocks, the ingredients of which have 
arranged themselves in layers or planes according to the 
direction in which the mass while still molten was moving. 
The same view was at first adopted and published by M. 
Renard. He now, however, expresses himself more 
doubtfully on the subject, and indeed is rather inclined 
to class the rock among the crystalline schists. 
Now the importance of the point in question will be at 
once perceived when it is stated that if St. Paul’s Rocks 
belong to the series of schists, they must once have lain 
deeply buried beneath overlying masses, by the removal 
of which they have been revealed. They would thus go 
far to prove the former existence of much higher and 
more extensive land in that region of the Atlantic; land 
too, not formed of mere volcanic protrusions, but built up 
of solid rock-masses, such as compose the framework of 
the continents. If, on the other hand, the rock is vol- 
canic, then the islets of St. Paul belong to the same order 
as the oceanic islands all over the globe. 
M. Renard reviews the arguments so cautiously that 
only towards the end do we discover him rather inclining 
to the side of the crystalline schists. With all deference 
to so competent an authority, however, we venture to 
maintain that the balance of proof is decidedly in favour 
of the volcanic origin of the rock. In the first place, as 
the distinguished Belgian petrographer himself admits, 
the law of analogy would lead us to expect the peridotite 
of St. Paul to be a volcanic protrusion. So cogent, 
indeed, is the argument on this head that. unless some 
irrefragable evidence against it is furnished by the rock 
itself, it must be allowed to decide the question. When 
the rock is studied under the microscope it presents 
precisely the banded fluxion-structure of true lavas, 
thus corroborating the inference of a volcanic origin for 
the mass. To say that this structure also resembles the 
“foliation of true schists is to repeat what may be remarked 
of hundreds of examples of undoubtedly eruptive rocks. 
Unless some peculiarity can be shown to exist in the St. 
Paul’s rock inconsistent with the idea of its being a 
volcanic extravasation, we are surely bound to regard it 
as no exception to the general rule that all oceanic 
islands are fundamentally of volcanic origin. M. Renard, 
however, fails to adduce any such peculiarity. He 
appears to have been led to doubt the validity of his first 
conclusions, and, be it also remarked, those of other 
observers, by finding so many published instances of 
peridotic rocks among the crystalline schists. A bed of 
peridotite among a group of schists, however, need not 
be of contemporaneous origin, any more than an intrusive 
sheet of basalt can be supposed to have been deposited 
at the same time and by the same processes that produced 
its associated sandstones and shales. Synchronism is 
not necessarily to be inferred from juxtaposition. We do 
not mean to dispute the assertion that some peridotites 
belong to the series of crystalline schists. But others are 
most assuredly eruptive rocks. It is among these that 
we should naturally seek for analogies with the rock of 
St. Paul. 
To sum up the reasoning we may infer that, judging 
from the structure of other oceanic islands, the ma- 
“NATURE 
[Mov. 9, 1882 
terial comprising the rock of St. Paul should be of — 
volcanic origin; this inference is confirmed by chemical 
and microscopical analysis, and especially by the dis- 
covery of a minute structure in the rock identical with 
that of many lavas, though a similar structure can be 
recognised in some schists ; the islets of St. Paul furnish 
therefore no evidence of an ancient land having formerly ~ 
existed in the middle of the Atlantic Ocean, on the con- 
trary they have probably been built up on the submarine 
Atlantic ridge by long continued volcanic eruption like 
the other islands of the same. Ocean. ; 
The exhaustive methods of research employed by M. 
Renard in the study of the rock of St. Paul furnish an 
excellent illustration of the great strides made in recent 
years by petrography. The other rocks collected by the 
Challenger Expedition are to be treated in the same 
manner, but it is understood that instead of being thrown 
into separate Reports the petrographical details will be 
interspersed through the ‘‘ Narrative’ at the places 
where the localities are described. These contributions 
will form not the least important parts of this great work, 
the advent of which has been so long and so patiently 
waited for. ARCH. GEIKIE 
THE LIFE OF CLERK MAXWELL 
The Life of James Clerk Maxwell, with a Selection from 
his Correspondence and Occasional Writings, and a 
Sketch of his Contributions to Science. By Lewis 
Campbell, M.A., LL.D., Professor of Greek in the 
University of St. Andrews, and William Garnett, M.A., 
Late Fellow of St. John’s College, Cambridge, Professor 
of Natural Philosophy in University College, Notting- 
ham. 
Te volume will be heartily welcomed by all who 
knew Clerk Maxwell, and who cherish his memory, 
and by the still wider circle of those who derive pleasure 
and new vigour from the study of the lives and work of 
the great men that have gone before them. 
The work consists of three parts, a biography with 
selections from Maxwell’s correspondence, a popular 
account of his scientific work, and a selection from his 
poetry, both juvenile and of later years, including the 
serio-comic verses on scientific subjects, some of which 
are already so well known. 
The biography is mainly the work of Prof. Lewis 
Campbell, whose schoolboy friendship and life-long inti- 
macy with Maxwell amply qualified him for the task. 
As far as vicissitudes of fortune are concerned, the life 
of Clerk Maxwell was absolutely uneventful. Worldly 
struggles he had none ; from the very first he was warmly, 
if not always quite fully, appreciated by all whose good 
opinion he could have valued; promotion such as he 
cared for came almost unsought, and scientific distinction 
of the honorary kind was conferred upon him unstintedly 
while he lived to enjoy it. But in truth all these things 
moved his serene spirit as little as they disturbed his 
outward life; the interest of his biography lies in tracing 
the growth of a mind which was dedicated, literally from 
infancy, to the pursuit of science, and which nevertheless 
neglected nothing becoming a man to know. For unity 
of aim and singleness of heart, for high-minded neglect 
of the worldly strife that is begotten of vanity, ambition, 
