THE ROYAL ARTILLERY INSTITUTION. 
415 
and the block of steel is then entirely surrounded with longer pieces of refuse wood 
thrown in from the top of the furnace. 
“ After the steel has acquired the proper uniform temperature throughout, the 
travelling crane is brought over the furnace; the cover belonging to the top of the 
furnace is then removed, after which a pair of large iron tongs attached to the 
crane fasten themselves at the top end of the steel block or tube. The tongs are 
so constructed that the heavier the weight, the tighter they grip the steel; still it 
is found necessary to turn a small collar upon the end of the block, to prevent the 
tongs slipping by the weight. After the tongs have fastened themselves upon the 
block of steel, it is drawn out of the furnace and sunk into a large iron tank 
about 20 feet deep, containing several hundred gallons of oil. The heated steel in 
passing into the oil will sometimes cause the surface oil to take fire, which, after 
the whole body of the steel is beneath the surface of the oil, is extinguished by 
closing the covers at the top of the tank, and spreading a piece of canvas over 
them. The tank has a water space around it in which a supply of cold water 
permeates for the purpose of keeping the oil cool. The best way to describe the 
tank is to state that it is an old steam boiler, sunk endways and perpendicular in 
the ground.” 
The process of toughening has a bad effect in two ways; it not only warps 
the steel a little, but frequently causes the surface to crack. The barrel 
must therefore be slightly turned and bored, to make it straight inside and 
outside, as well as to remove any flaws that may have been generated. This 
second boring (performed with a cylindrical boring head, fitted with five long 
edged cutters and five wood burnishers), increases the diameter to 8‘6 inches. 
The time required for second boring—slight as is the cut—is 25 hours^ 
the steel being much harder after toughening. By these means the cracks 
are generally removed, but several tubes have been rejected in consequence 
of flaws still appearing to penetrate to a dangerous depth, and lest there 
should be any not visible to the eye, the steel barrel is subjected as follows 
to the water test before referred to. 
The tube being recessed on the face for a gutfca percha ring, and inside 
the muzzle for a leather cup, is fitted with these washers and placed in a 
horizontal hydraulic press, and screwed tightly up between two cast-iron 
heads by means of two strong wrought-iron bars, extending from head to 
head, and fitted with nuts at the outside, worked by a long spanner. The tube 
is then filled with water from the main through the hole in head and leather 
cup, and then the pipe of the press is fixed into the hole, and the pump is set 
to work by steam. The pressure on the interior is shown by two indicators, 
one vertical and one horizontal, so as to check one another. When 3^ tons 
per square inch is thus indicated, the pressure is withdrawn, and if no flaw 
has been detected by the formation of moisture on the exterior, the tube is 
considered safe and sound. The barrel is left in this state until the B tube 
is ready to be shrunk over it. 
The B Tube. 
The B tube is composed of two single and slightly taper coils united 
together. The first coil is formed of two bars joined together—one 16 feet 
long and x 4f" x 4§" in section, the other 33 feet by 5" x 4-|" x 4". 
The second coil is also composed of two bars—one 18 feet by 44" x 4J" x 4"* 
and the other 31 feet by 4" x 4" x 3V'- 
