3. The summit of the mountain has been lowered and 
flattened. 
An examination of the lava of 1872 does not appear likely 
to lead to any new results. Its mineralogical nature is 
essentially the same as that of the other lavas of all ages 
that have been found both on Vesuvius and in La Somma. 
It is composed of a leucitic rock strewn with crystals of 
augite, and destitute of vitreous felspar; whence the 
names of leucitiferous or augitiferous, as one or other 
substance prevails. The most ancient lava which forms 
the body and crevices of La Somma, is in general 
very pale; it often contains an abundance of leucite 
crystals of the size of a foot ; but its composition is, quali- 
tatively, essentially analogous to that of the actual black 
lava. The lava of 1872 differs considerably in its 
physical appearance from that of 1858, The last is 
much less scoriated; it has a fleecy surface formed of 
round embossments, shining and comparatively little 
roughened. We might liken it to black whipped cream, 
which has flowed along, forming arches, fibrous stalactites 
twisted cords, which look at places as if vitrified. The 
lava of 1872, on the contrary, is extremely scoriaceous, 
and assumes a form almost like madrepore. On account 
of the great shrinking of the material, it has been broken 
up into blocks, entirely separated from each other, 
and roundish, because the mass was as yet vitreous ; 
porous, in consequence of the quantity of gas it enclosed, 
and full of the most curious irregularities resembling 
coral and vegetation, which render progress infinitely dif- 
ficult. The difference of appearance, combined with a 
thin layer of gray cinders which adheres to the lava of 
1872, enables one to distinguish at once between it and 
those of preceding years, It will be noticed also to the 
north of the Observatory that the current has filled all the 
bottom of the valley of Ventrana, while on the south it 
has only run into the crevices of the old lava, surrounding 
the knolls, separating, re-uniting, leaving here and there 
inlets, as rivers without any determinate bed do at low 
water. This difference of structure of the two lavas 
seems to result from the very rapid cooling of that of 
‘1872. 
It is not easy to form a notion of the depth of this lava. 
In the lower parts the bed is about eight metres deep, 
with a breadth of about 800 metres; its borders form 
moraines of 45°, which indicate the: small fluidity of the 
matter at the time it reached the place. In Atrio del 
Cavallo the moraine of the bed of lava which leans against 
the foot of the rocks of La Somma is less elevated, but 
the enormous waves in the middle of this surface argue in 
some places a considerable thickness. 
The successive eruptions which have taken place in 
Atrio and which have piled up layer on layer, have enor- 
mously raised the level of the ground. A German geo- 
logist has conceived the idea of counting the layers which 
form the vertical dykes on the rocks of La Somma. At 
present the number would be hidden beneath more than 
a hundred feet of lava. The stream which debouches 
from Atrio has ended by considerably overtopping the 
Observatory ; and that the latter has not been threatened 
this year results from the fact that the saddleback of 
Monte Canteroni, upon which it stands, rises in the direc- 
tion of Vesuvius in such a manner that its eastern ex- 
tremity (Croce del Salvatore) has hitherto performed the 
NATURE 
part ofa buttress in dividing the burning stream and divert- 
ing the two currents into the ravines which slope rapidly 
to the right and left of the height. But a new outbreak 
will, without doubt, sweep away the eastern extremity of 
this crest, and a succeeding one would easily be able to 
send a stream of lava flowing as far as the Observatory. 
Foreseeing this danger, M. Palmieri has raised above the 
building a redan of a'very sharp angle. This will form but 
a weak barrier, though it may be able to retard for a little 
the progress of the devastating element. Since several of 
more or less in danger. Let us hope, however, that 
when that time arrives a worthy successor of Palmieri 
may safely chronicle what is going on, and that another 
De Saussure may be there to see. 
WAGNER'S HANDBOOK OF CHEMICAL 
TECHNOLOGY 
A Handbook of Chemical Technology. By Rudolph 
Wagner, Ph.D. Translated and edited from the eighth 
German edition, with extensive additions by William 
Crookes, F.R.S. (London; J. and A, Churchill, 1872.) 
VERY one who has studied chemistry from a scien- 
tific point of view must have been more or less 
struck with the fact that nearly all our manuals of 
chemistry have much of their space occupied with de- 
tailed descriptions fof various manufacturing processes, 
and many must have asked why this is. It is not easy to 
see what utility there is in describing, in works professedly 
devoted to a scientific subject, such processes as those for 
the manufacture of chamois leather, wine, vinegar, china 
and earthenware, &c. &c.; and yet our largest and most 
ambitious manual, in common with its smaller com- 
panions, devotes scores of its pages to the consideration 
of such subjects. This fashion is much to be deprecated 
for many reasons: in the first place, these processes are 
utterly useless to the student, as, in the majority of cases, 
they illustrate no rule, elucidate no reaction. In the 
second, it is utterly impossible to do full justice to them 
in the space to which they must perforce be confined ; 
and in the last, much valuable matter about the rarer 
elements and reactions is squeezed out of place altogether, 
or passed over with a mere mention. 
This system has borne its natural fruit in the numberless 
questions bearing on manufactures which are to be found 
in all our chemical examination papers ; and the result is, 
that many a man passes with credit on the marks gained 
by answering such questions, while others who, perhaps, 
have a much better knowledge of the science, fall behind 
in the race, because they have not devoted their time to 
Technology. 
It is not difficult to see how this state of things arose, 
It is not so many years (we were almost going to say 
months), since chemistry was regarded by the public 
much in the same way that they now look upon the 
‘ 
the recent eruptions have happened on the Atrio side, it 
would seem as if the chief centre of volcanic action was 
tending towards that point, and there seems little doubt 
that one of the next eruptions will place the Observatory 
higher mathematics, as something very mysterious, very 
good for a learned man to know—but utterly useless and 
“unpractical” for all ordinary purposes. Such being the ~ 
