424 MOLESWORTH'S PQCKET-BOOK
tured point should scratch glass. To test its tough-
ness, place a fragment on a block of cast iron; if
good it may be driven by the blow of a hammer into
tlie cast iron, if poor it will prush under the blow.
Tests of Iron. ■
A soft, tough iron, if broken gradually, gives long silky
fibres of leaden-grey hue, which twist together and cohere
before breaking
A medium even grain with fibres denotes good iron.
Badly-refined iron gives a short blackish fibre on fraeture.
A very flue grain denotes hard steely iron, likely to be cold,
short, and hard.
Coarse grain with bright crystallized fracture or discoloured
spots denotes cold-short, brittle iron, which works easily when
heated and welds well. Cracks .on the edge of a bar are indi-
cations of hot-short iron. Good, iron is readily heated, is soit
under the hammer, and throws out few sparks.
WORKSHOP RECIPES.
Antifriction Grease.
Boil together, If cwt. of tallow with 1| cwt., of
palm oil. When boiling point is reached allow it
to cool to blood heat, stirring it meanwhile, then
strain through, a sieve into a solution of | cwt. of
eoda in 3 gallons of water, mixing it well.
The above is for summer. __
For winter, 1| cwt. of tallow to If cwt. palm oil.
Spring and autumn, 1J „ 1J »
Foundry Reoipes.
Fire-clay crucibles, 2 Stourbridge clay,
1 hard gas-coke, finely
powdered..
Berlin crucibles, 8 Stourbridge clay,
3 old crucibles, ground finely,
5 coke,
6 graphite, or “ black-lead ”
Black-lead crucibles, 1 fire-clay,
2 graphite.