THE ROYAL ARTILLERY INSTITUTION. 
127 
these are costly to manufacture, care has to be taken to avoid it; but the metal 
should be as hot as it possibly can be without injury to the chill. 
There are some peculiarities about molten hard iron. The break, when 
a rod is drawn over its surface, is peculiar—forming long lines or ridges, very 
different to the star-like break of soft iron. It throws off more sparks; but 
a more important peculiarity, which affects manufacture, is that it is not so 
fluid as the soft iron, and it soon passes into a pasty viscous condition, and 
contracts nearly double as much as soft iron in cooling. It melts at a lower 
temperature than grey or soft iron. 
The chills in which the heads of the projectiles are cast are turned from 
cast-iron to the required ogival shape, the head being struck with a radius of 
1J diameters. They form a lining to larger blocks of cast-iron, so as to 
avoid the expense of re-casting a large mass of metal when a chill wears out. 
(A chill for a 10-in. will last about 70 castings; the lining costs about 50s.) 
The chill warps and sometimes becomes flawed after it has been in use, 
and if the iron is put in too hot a new chill may be spoiled at once. Holes 
are made through the chill to receive two steel rods, wdiich form the extractor 
holes. With all natures, except the 11-in. and 12-in. 35-ton, holes are 
made in the chills to receive the loam cores which form the recesses for the 
buttons; small holes, leading to a groove cut in the large block, form gas 
escapes for the gas from the buttons. 
Chills add to the expense of casting. As the final shape is given by them 
to the head, they have to be replaced when only slightly damaged. 
Before use, the chills are cleaned out with water, and are smeared with 
tallow and China-clay, which fills up any cracks in the chill. The chills are 
made larger than the head, to allow for the shrinking of the projectile in 
cooling. 
As Palliser projectiles are cast as near as possible to their final dimensions, 
greater care is taken in incorporating the sand and coal-dust used for 
moulding than when casting other shells. It is passed under revolving cast- 
iron runners, which thoroughly mix up the ingredients. 
The mould contains the body and base of the shell. It is formed by 
placing two cast-iron moulding-boxes (which are keyed together, fastening 
on to one another with a recessed joint, and pierced with holes to allow the 
gas from the heated coal-dust to escape), over a “ pattern ” of the shell. 
The “ pattern ” resembles the shell, but is a very little larger in diameter, 
so that the casting is slightly larger than the finished projectile. It is so 
arranged as to easily run up or down through the moulding table, and is 
fitted with studs which can be turned in and out, and which form recesses in 
the mould into which loam cores can be fitted. From the top of the 
pattern a cylindrical rod projects, which forms a hole in the mould through 
which the spindle of the core passes. 
The pattern being run up and its studs turned out, the moulding-boxes 
being over them, sand and coal-dust are rammed in carefully with iron rods 
until the moulding-box is filled; holes being made to form the “runner ” 
and “riser” by inserting two sticks which touch the base of the pattern. 
These holes allow the metal to flow in and rise when the shell is cast. The 
depth of the upper box is almost purely taken up by these holes ; so the 
metal, when poured in, rising in these holes, forms a kind of dead head to 
the shell. When the ramming of the sand is finished, the buttons of the 
pattern are turned in, the pattern lowered, and the mould removed. 
