78 
POPULAR SCIENCE REVIEW. 
other writers. There is, if we may he excused the expression, a tone of 
bitterness all through his writing, which gives the reader a most uncom- 
fortable sensation, and which leads a person who is altogether unbiassed to 
imagine a feeling of jealousy on the part of so distinguished a writer as 
Mr. Mallet, which we are sure cannot exist in reality. After giving a 
sketch of the various authors who have ventured to give different and 
erroneous opinions on the subject of vulcanicity, the writer gives himself 
the following definition of an earthquake, it being the same which he has 
supplied in his original memoir in the Transactions of the Koyal Irish 
Academy ” : — “ The transit of a wave or waves of elastic compression, in 
any direction, from vertically upwards, to horizontally, in any azimuth, 
through the crust and surface of the earth, from any centre of impulse or 
from more than one, and which may be attended with sound and tidal waves, 
dependent upon the impulse and upon circumstances of position as to sea 
and land.” And, having given this definition, we may leave the editor of 
the work for the present, as any attempt to enter upon the numerous and 
cleverly- stated arguments which he advances would be to extend our notice 
to an unimaginable space. We therefore pass on to Professor Palmieri’s 
admirable account of the eruption. In the first place, we are informed of 
what we assuredly did not know before, viz., that the Italian Professor 
foretold this great eruption: for he says it was the last phase of the 
eruption which began in the end of January 1871, or, in his own words. 
An account of which I was unwilling to write, because I was convinced 
that it would not really terminate without a more or less violent explosion, 
such as I have often predicted.” From this period all through the year, 
and the four first months of the succeeding year, the Professor watched the 
mountain giving out its different discharges, and he observes that on the 
23rd, 24th, and part of the 2oth of April it was an excessive action ; but 
then that it remained nearly quiet till the morning of the 26th of the 
same month. At which time, the Professor observes, “Numbers of visitors, 
attracted by the splendour of the lava-streams of the preceding night, 
which they supposed still continued, soon arrived ; but finding them ex- 
hausted, were for the most part conducted by their guides to see the one 
still flowing. It was almost inaccessible, and to reach it one had to walk 
over the rough inequalities of the scoriae. It took me two hours to get 
there from the Observatory, when I visited it that morning, and therefore I 
endeavoured to dissuade those who wished to visit it at night from the at- 
tempt, but set out myself from the Observatory at 7 p.m., leaving my only 
assistant there. The instruments were agitated. After midnight the Ob- 
servatory was closed, and my assistant retired to rest. Late and un- 
lucky visitors passed unobserved with an escort of inexperienced guides ; 
at half-past three o’clock in the morning of the 26th they were in the 
Atria del Cavallo, when the Vesuvian cone became rent in a north- 
westerly direction, the fissure commencing at the little cone which dis- 
appeared, and extending to the Atria del Cavallo, whence a copious 
torrent of Java issued. Two large craters formed at the summit of the 
mountain, discharging numerous incandescent projectiles, with white ashes 
and glittering with particles of mica, which frequently recurred. A cloud 
of smoke enveloped these unfortunates who were under a hail of burning 
