POWER OF LITHARGE, ETC. 273 
that this excess of litharge contains sulphuretted, oxidisable 
elements. 
Ought the solution of oxygen in a liquid in igneous fusion, 
and possessing no chemical action on the gas, to be consid- 
ered as a general, phenomenon, or merely confined to lith- 
arge and silver? It is a question, the experiments I propose 
to make may perhaps solve. The phenomenon is connect- 
ed, perhaps, with questions arising out of geology, and con- 
sequently deserves an attentive study. 
Not to wander from the subject of this note, I shall con- 
fine myself, for the present, to the examination of what 
passes in the centre of the masses of melted litharge when 
it leaves the furnace, and to the discussion of the part the 
imprisoned oxygen may play in these masses that become 
solidified, and end in changing, by degrees, their internal 
structure. 
At Poultaouen, the litharge, when it leaves the furnace, 
and when it has acquired a sufficient degree of purity, is 
collected in iron pots of a conical form, and holding about 
30 litres. The litharge is not long before it becomes solid 
on the surface, and it is then of a yellow or greenish yellow 
color; at the end of a few hours, sometimes at the end of 
half an hour, the mass breaks and splits in every direction, 
becoming a friable crystalline mass, possessing a deep red 
color ; the crust, which had become suddenly solidified? 
alone preserves its color and coherence. The red litharge 
only, which is carefully picked out, is fit for sale j the yel- 
low litharge is placed apart, to be revivified. 
Sometimes the phenomenon takes place more quickly ; a 
sort of explosion occurs, which, in the first instance, 
separates the conical mass of litharge into a number of large 
blocks, at the same time there is a projection of a certain 
quantity of litharge, which had remained liquid, or in a pasty 
state in the interior. 
It appears to me to be probable enough that the oxygen 
imprisoned while the solidification was going on, acts me- 
