Analyses of Books. 
179 
not into three but into two distinct strata. The upper one was water ; the under 
one pliosphuret of sulphur ; and between both was observed a white powder which, 
when exposed to the sun’s rays, exhibited ail the colours of the prism, and was there- 
fore supposed to he a multitude of little crystals. 
In the repetition of the experiment, under the idea of obtuiniuglarger crystals, the 
shaking was omitted. In three months the two lower liquids appeared to form but 
one There was now a difficulty to separate the supposed formed diamonds from 
the pliosphuret of sulphur, ou account, of the inflammability of the latter. It was 
howerer at last effected ; and M. Gtinnal was rewarded by finding several crystals, 
twenty of which were large enough to be taken up on the point of a penknife, and 
three were as large as a grain of millet. These last having been submitted to the 
inspection of an experienced jeweller in Paris, they were pronounced to be real 
DIAMONDS. 
Analyses of Books. 
Transactions of the Geological Society of London: Second Series , Vol. ii. 
Part 3d. 
The 1st and second parts of this volume have been published some time. The third 
part, being the conclusion of the volume, has just reached us ; and as it contains 
some papers that will be considered in India rather interesting, we hasten to give an 
sccount of them. 
XXII. On the volcanic District of Naples. By G. Poulett Scrope, Esq. F. G. S. 
T. ff. S. 3*c. pp. 337 to 332. 
Mr. Scrope is the author of a work on volcanoes, which has attracted a great 
deal of attention, and in which a very clear and full account of the several pheno- 
mena is followed liy a view of the author’s hypothesis or mode of explaining these 
appearances. He lias published also several shorter papers on subjects connected 
with volcanoes or volcanic rocks ill the Transactions of the learned body of which he 
is a member, as well as in some of the scientific journals of the day. The import- 
ance of the subject begins to be generally acknowledged. Nor can there be a 
stronger proof of its increasing interest, than the fact of a geologist like Mr. Scrope 
Hiring so much of his attention to it. A great revolution has taken place since the 
time when volcanoes were considered mere local phenomena, and were supposed to 
*)c explained by the casual inflammation of beds of coal. The discovery of the 
metallic bases o'f the earths has thrown a strong light on the causes of these pheno- 
mena ; while their number, so much greater than had been supposed, gives new views of 
the importance of the part they play in the great scheme of nature. The identity of 
origin with ordinary volcanic products of the extensive class of trap rocks begins to 
tic more than surmised ; and to the admirers of that original genius that prompted 
Hie Huttonian theory, nothing can be more gratifying than the daily strength that 
theory is gaining as' facts accumulate, and appearances are more studied. Wlmt 
ran be more favml able to the truth of a theory than the fact, that nlmostevcry now 
discovery adds strength to it, and removes some ill considered objection r Thus, whe- 
ther, with Sir Janies Hall, we view the curious modifications of the ordinary pheno- 
mena of heat under extraordinary pressure ; or, with Sir Humphry Davy decompose 
those substances, till his time considered simple, and view them so greedy ot oxygen 
that they take it from water or even iee, bursting out into flame from the rapidity ot 
the combustion; in each case we are struck with the triumphant nature ot the an- 
s » er, which the knowledge of these facts would have enabled the eloquent defender ot 
the Huttonian theory to give to those who could so little weigh the value of two rival 
theories. But to return from this digression. 
Mr. Scrope in the present paper proposes to give an account of such phenomena, 
observed in the volcanic district of Naples, as hax-e been overlooked by preceding 
geologists, Menard de laGreye, Necker de Saussure, Bneshik, and more lately Dr. 
Haubeuy. He considers the volcanic district of Naples to include not only 
Soninia, Vesuvius, the coast of Sorrento, and the immediate environs ot Naples, 
Pozzuoli, and luma; hut also the islands ot 1‘rocida and Ischia, with which they 
are as closely connected in composition as in geographical situation. This linear 
groups, which ranges N. E. to S. W-, is terminated at ei her extremity by thetwo 
Principal volcanic mountains of Ischia and Vesuvius, lhc latter as I have mentmn- 
«1 in a previous memoir, seems to he in communication with the group of Albano 
and Home, through the intervention of the Rocca Monfina and ot Ur miuoi vents 
of volcanic matter scattered along that remarkable longitudinal valley, which 
