oke more easily than those from No. 2, and so on until those made
from No. 4 were tested, when the maximum strength was reached. No. 4 pig
iron was in fracture a pale gray, bordering on mottled. Several points
regarding foundry operations in the production of chilled castings were
raised for discussion. They embraced the depth of chill to be imparted to
chilled rolls and railway wheels, and in the case of traction wheels, the
width of chill in the tread; preparation of the chills--by coating with
various carbonaceous matters, lime, beer grounds, or, occasionally, some
mysterious compost--and moulds, selection and mixture of pig irons, methods
and plant for melting, suitable heat for pouring, prevention of
honeycombing, ferrostatic pressure of head, etc. Melting for rolls being
mostly conducted in reverberatories, the variations in the condition of the
furnace atmosphere, altering from reducing to oxidizing, and _vice versa_,
in cases of bad stoking and different fuels, were referred to as
occasionally affecting results. Siemens' method of melting by radiant heat
was mentioned for discussion. For promoting the success of a chilled roll
in its work, lathing or turning it to perfect circularity in the necks
first, and then turning the body while the necks bear in steady brasses,
are matters of the utmost importance.

The author next referred to the great excellence for chilling purposes
possessed by some American pig irons, and to the fact that iron of a given
carbon content derived from some ores and fluxes differed much in chilling
properties from iron holding a similar proportion of carbon--free and
combined--derived from other ores and materials. Those irons are best which
develop the hardest possible chill most uniformly to the desired depth
without producing a too abrupt line of division between the hard white skin
and the softer gray body. A medium shading off both ways is wanted here, as
in all things. The impossibility of securing a uniform quality and chemical
composition in any number grade of any brand of pig iron over a lengthened
period was adverted to. Consequent from this a too resolute faith in any
particular make of pig iron is likely to be at times ill-requited.
Occasional physical tests, accompanied with chemical analysis of irons used
for chilling, were advocated; and the author was of opinion it would be
well whenever a chilled casting had enjoyed a good reputation for standing
up to its work, that when