- oe SEC SS ae eee ee» ye 
se ae patie i poise ; 
sk NATURE 
and the respective electrical conditions of the smoke and 
ashes. 
The report is illustrated by eight plates of the instru- | 
ments employed at the Vesuvian observatory, and of views 
of the eruption in its different stages, which latter, how- 
ever, as is frequently the case when taken from photo- 
graphs, cannot be regarded as altogether satisfactory ; 
the translation is done with evident care, but the nomen- 
clature is open to objections, especially when such terms 
as sulphide of potash and ferrochloride of ammonia are 
encountered. 
The introductory sketch by which the translation is 
prefaced, occupies 90 out of 148 pages, and must 
be regarded as quite a distinct treatise, being only in- 
directly connected with the report on Vesuvius ; and 
its style, which cannot be regarded as an agreeable 
one, is not very gracious to the labours of the many 
| eminent men who have preceded or now hold views 
differing from those of the author. Although brought — 
forward as representing the present state of knowledge of 
terrestrial vulcanicity, we find no reference to any of the 
continental men of science, who have done so much in this 
direction, and it should be more correctly entitled an 
exposition of the author’s views on seismology and what 
he terms vulcanology, the first 46 pages being but an ab- 
stract of his previously published investigations into the — 
phenomena of earthquakes. 
The second part of this sketch is a resumé of the 
7 
Vesuvius, on April 26, 1872, from a Photograph. 
took the direction of the Camaldoli 
main features of Mr. Mallet’s dynamical theory of 
volcanic energy, published in the Proceedings of the 
Royal Society for 1872, a hypothesis which explains 
volcanic action as originating in the secular cooling 
of our globe, when, to use the words of the abstract, 
“As the solid crust sinks together to follow down 
after the shrinking nucleus, the work expended in mutual 
crushing and dislocation of its parts is transformed into 
heat, by which, at the places where the crushing suffi- 
ciently takes place, the material of the rock so crushed, 
and that adjacent to it, are heated even to fusion. The 
access of water to such points determines volcanic erup- 
tion.” To one who, like Mr. Mallet, assumes that heat, 
and heat alone, is in the first instance all that is required 
x The Observatory.—2. Fossa della Vetrana. V 
Surface of the Lava. 4. The Novelle, St. Sebastiano, and Massa. 5. Lava which took the direction of Resina. 6. Lava which, from the Crater, 
7. The Grain Stores, near Naples. 8. Resina. 
3. Eruption of Smoke and Ashes, with Stones, from the 
9. Torre del Greco. to. The Camaldoli. 
to account for the varied phenomena of volcanic activity, 
this explanation may appear satisfactory enough, although 
even if it be proved experimentally that the intensity of 
| the heat thus produced in such cracks of contraction, or 
faults, as a geologist would probably term them, is suffi- 
cient to fuse the substance of therocks in immediate contact, 
it would nevertheless be found even still more difficult to 
account for the quantity of heat requisite to melt up such 
vast volumes of rock matter as are known to proceed from 
volcanoes. Allowing, however, that even this difficulty 
can be satisfactorily explained away—and it is admitted 
that the conversion of the mechanical force into heat is 
sufficient to effect the melting part of the operation—there ~ 
remains the still greater difficulty of explaining the chemi- 
4 
