ON MANGANESE BRONZE. 381 
No. 2 is similar to No. 1, but still stronger, and it can with the 
required care be cast in sand, when it is required to produce castings 
for special purposes, possessing the greatest strength, hardness, and 
toughness, but it must be melted in crucibles; passing it through the 
‘reverberatory furnace injures the metal, and causes unsound castings. It 
is not, therefore, adapted for general brassfounders’ purposes, and those 
only who understand its peculiarities and are experienced in its use 
should attempt casting it insand. One of the most important applications 
of this quality is that of producing articles cast in metal moulds under 
pressure. Blocks of this metal thus simply cast have all the characteristics 
of forged steel, as regards strength, toughness, and hardness, without any 
of its defects. It is perfectly homogeneous, and, while not possessing a 
fibrous texture, derived from rolling or hammering, it is still fibrous in 
character, and this in not one but in all directions alike, and when broken 
shows a silky fracture. Its tensile strength is from thirty to thirty-five 
tons per square inch, its elastic limit from sixteen to twenty-two tons, with 
an ultimate elongation of from 12 to 22 percent. It can be cast on to 
any object, and will shrink on to it with a force equal to its elastic limit, 
and when released will show an amount of resilience about double that 
of steel. Thus a hoop shrunk on to a solid cylinder of iron gave the fol- 
lowing results :—It stretched when hot -03 of its diameter in the process 
of contraction, and when cold and relaxed sprang back about ‘003 of its 
diameter. As regards hardness, it is about equal to mild steel. To 
compare it with gun-metal, wrought iron, and steel in this respect, the 
following tests were made, by forcing a knife-edged angular die into the 
flat surfaces of each of these metals. To make a dent of equal length, 
the following pressures were recorded :— 
Gun-metal . 3 = = A . F - - . 12 cwts. 
Wrought iron , : 3 : : : : - np alte Fee 
Mild steel % 3 : é 6 £ x : : pe Oe 
Mild steel, oil hardened. F : 3 z : ‘ PAQBIG 
Manganese bronze, as cast A 3 2 : L SAO a9 
Manganese bronze as cast hardened by cold pressure . 22to23 ,, 
All these results point to this material as a most suitable one for the con- 
struction of hydraulic and other cylinders required to stand great strains, 
and particularly for ordnance. 
The Manganese Bronze and Brass Company are now making arrange- 
ments for casting a block of this metal, to be made into a gun; and the 
results are being looked forward to with much interest, as, should this 
prove successful, the material is likely to become a formidable rival to 
steel and iron for the construction of artillery ; for, although the metal 
itself is more costly, the simple way in which it can be manipulated 
will make the total cost less, and the time required to construct heavy 
guns of it will probably be less than one-fourth of that required to build 
up iron or steel guns. 
No. 3. This is an equally important alloy with the last, but possessing 
altogether different qualities, and suited to different and more varied 
applications. It is composed principally of copper and tin in about the 
proportions of gun-metal, combined with a considerable dose of ferro- 
mangauese. Its chief characteristics are very great transverse strength, 
toughness, and hardness, the facility with which it can be cast, and the 
soundness and uniformity of the castings produced, without any special 
