a couple of hours per day, and that not very regularly." ("L.L." I.
page 321.) Darwin's work on the various volcanic islands examined by
him had given him the most intense pleasure, but the work of writing
the book by the aid of his notes and specimens he found "uphill
work," especially as he feared the book would not be read, "even by
geologists." (Loc. cit.)

As a matter of fact the work is full of the most interesting
observations and valuable suggestions, and the three editions (or
reprints) which have appeared have proved a most valuable addition to
geological literature. It is not necessary to refer to the novel and
often very striking discoveries described in this well-known work. The
subsidence beneath volcanic vents, the enormous denudation of volcanic
cones reducing them to "basal wrecks," the effects of solfatarric action
and the formation of various minerals in the cavities of rocks--all
of these subjects find admirable illustration from his graphic
descriptions. One of the most important discussions in this volume is
that dealing with the "lamination" of lavas as especially well seen in
the rocks of Ascension. Like Scrope, Darwin recognised the close analogy
between the structure of these rocks and those of metamorphic origin--a
subject which he followed out in the volume "Geological Observations on
South America".

Of course in these days, since the application of the microscope to the
study of rocks in thin sections, Darwin's nomenclature and descriptions
of the petrological characters of the lavas appear to us somewhat crude.
But it happened that the "Challenger" visited most of the volcanic
islands described by Darwin, and the specimens brought home were
examined by the eminent petrologist Professor Renard. Renard was so
struck with the work done by Darwin, under disadvantageous conditions,
that he undertook a translation of Darwin's work into French, and I
cannot better indicate the manner in which the book is regarded by
geologists than by quoting a passage from Renard's preface. Referring
to his own work in studying the rocks brought home by the "Challenger"
(Renard's descriptions of these rocks are contained in the "Challenger
Reports". Mr Harker is supplementing these descriptions by a series of
petrological memoirs on Darwin's specimens, the first of which appeared
in the "Geological Magazine" for March, 1907.), he says:

"Je dus, en me livrant a ces recherches, suivre ligne par ligne les
diver