1854.] OF THE ROYAL INSTITUTION. 439 
cinder on the other hand, such as was flowing from No. 1, is thick, 
runs from the tap-hole with difficulty, has a dull, nearly black colour, 
and is very heavy; in fact analysis shows that it contains 20 per 
cent. of oxide of iron. The cinder from the gray or foundry iron 
furnace has altogether a different appearance, but both white and 
gray cinders are nearly as interesting to the chemist and mineral- 
ogist, as they are to the iron manufacturer, They are received from 
the furnace in large iron boxes, whence, as soon as they have 
solidified, they are removed on railroads to be used for the construc- 
tion of roads, rough walls, &c. The outside of the cinder lumps, 
*‘donkeys”’ as they are called by the workmen, have a vitreous 
fracture ; but the interior, where the cooling process has taken place 
very slowly, is stony, and usually contains cavities which are lined 
with crystals; those from white iron have a composition which 
places them among the pyroxene or augite class of minerals; those 
from grey iron are more nearly allied to idocrase. [Reference was 
here made to a Table giving the per centage composition of three 
varieties of crystalline slags obtained from the Cwm Celyn works.]} 
The iron from the blast furnace is usually “tapped” twice in 
twenty-four hours ; the liquid metal is either received into moulds 
where it assumes the form of semi-cylindrical bars, technically called 
“pigs,” or it is run into wider channels from which, after being 
broken up, it is removed directly to the “ refinery.” 
The “cinders ” alluded to in the above statement of the mineral 
burthens of the two Cwm Celyn furnaces, are not the cinders of the 
blast furnace, but “forge cinders ;’’ that is, the cinders that separate 
from the cast iron during the processes of “ refining,” ‘ puddling,” 
and “ balling,” by which the cast iron is converted into wrought 
iron. These cinders are very rich in iron, which exists principally in 
the form of silicate of the protoxide; they often occur beautifully 
crystallized, particularly after they have been “ calcined,” an operation 
which is now always performed on them in well conducted works, 
and which has for its object the removal of the sulphur and the 
peroxidation of a portion of the iron: the tendency of sulphur even 
when it exists in iron in very small quantity, is to make the metal 
what is called “hot short,” so thatit cannot be worked under the 
hammer ; the tendency of phosphorus, another element always found 
in “forge cinders” is to make the iron “ cold short,” so that it 
breaks on attempting to bend it. The separation of sulphur, by 
calcining, is very perfectly effected, and it is interesting to trace the 
process of its gradual elimination; in some places large masses of 
prismatic crystals of pure sulphur are seen, but usually nearly the 
entire surface of the heap is covered with a thin layer of sulphate 
of iron, sometimes crystallized, but generally in various stages of 
decomposition ; lower down in the heap, where the heat is greater, 
the sulphate of iron disappears, and in its place “ colcothar” is 
found. The separation of phosphorus from the forge cinders is still 
a desideratum. (Specimens of forge cinders, raw and calcined, crystal- 
EI 
