466 The History of Vesuvius fjuly, 
Portici, and Naples. On the 29th a strong wind blew from 
the crater towards the Observatory, and the scoriae broke 
some of the windows. Ashes accumulated to a depth of 
7J inches on the roof. Towards midnight the noise of the 
craters diminished ; the next day the detonations were few 
and far between ; and by May 1st, 1872, the eruption was 
completely at an end. 
On ascending to the summit of the cone Palmieri found 
the great crater divided into two parts by a wall with ver- 
tical sides 750 feet in height. The interior showed no sub- 
limations, but alternate beds of scoriae and compadt lava. 
Fumeroles emitting sulphurous anhydride, hydrochloric 
acid, and sulphuretted hydrogen at a temperature of 150° C. 
were found at the outside edge of the crater. 
Palmieri regards the great eruption of April 26th, 1872, 
as the la$t phase of the eruption which commenced early in 
1871. He calculates that the total amount of lava emitted 
amounts approximately to 20,000,000 cubic metres, about 
three-fifths of which was deposited on pre-existing lavas. 
Its destruction was estimated at 3,000,000 of lire. Among 
the products of the eruption were noted ; — Black oxide of 
copper, chloride of lead, chloride of iron, chloride of am- 
monium, chloride of calcium, and chloride of sodium. 
Traces of the chlorides of thallium and lithium were also 
detected. 
For some months after the dying-out of the eruption of 
1872 Vesuvius remained in a quiescent state, and the only 
manifest sign of the hidden fires appeared in the few fume- 
roles on the floor of the crater. These, however, gradually 
increased in number, the temperature rose, and steam and 
carbonic acid were abundantly evolved. Afterwards the 
carbonic acid diminished, and sulphurous acid made its 
appearance. Early in January, 1875, the writer ascended 
the mountain, and found the crater full of steam and sul- 
phurous acid. It was quite impossible to descend into it. 
As the wind from time to time blew the fumes over the edge 
of the crater we suffered from a feeling of suffocation, and 
violent coughing was produced. One of our party wore a 
pea-jacket of fluffy serge dyed with indigo, and the sul- 
phurous acid was in sufficient quantity to bleach it superfi- 
cially. 
Later in the year hydrochloric acid appeared — a sure sign 
that the volcanic activity was increasing. This gas is pro- 
duced by the adtion of silicates at a red-heat upon salt in 
the presence of aqueous vapour, and is a constant produdt 
of intense volcanic adtion in all parts of the world. To- 
