THE EOYAL ARTILLERY INSTITUTION. 
265 
EXPERIMENTS PERFORMED IN THE ROYAL GUN FACTORIES 
WITH 
“STEKRO METAL.” 
By JOHN ANDERSON, Esq. 
ASSISTANT SUPERINTENDENT, ROTA1 GUN PACTORIES. 
Composition of this alloy as made in the Arsenal at Yienna is, 
Copper 60, zinc 41*88, iron 1*94, tin *166. 
And as made at the Polytechnic, Yienna, its composition is, 
Copper 60, zinc 46*18, iron 1*93, tin *905. 
Alloys of a similar composition to that of the Austrian metal have been 
prepared in the Eoyal Gun Pactories, from which a better result has been 
obtained than from mixtures of the Austrian metal also prepared in the Eoyal 
Gun Pactories. The subjoined Table shews the results of the experiments 
with these different specimens. 
Composition. 
Treatment. 
Permanent 
elongation of 
*002 per inch. 
Breaking 
weight. 
Ultimate 
elongation 
per inch. 
Austrian mixture. 
As received . 
6*76 
26*75 
*1" 
R. G. Factories mixture of) 
copper 60, zinc 39, iron 3, > 
Cast in sand. 
11 
21*5 
•05" 
tin 1*5 . j 
Do. of copper 60, zinc 44, 
iron 4, tin 2 . 
do . 
13*75 
19*25 
*016" 
do do . 
Cast in iron . 
17*25 
24*25 
•016" 
do do . 
Cast in iron, and annealed... 
15*25 
23*25 
•02" 
do do . 
Forged red hot. 
17 
28 
•045" 
Note. —This alloy is said to he the invention of Baron de Rosthorn, of Vienna. It derives 
its name from a Greek word, signifying “ firm.” It consists of copper and spelter, with small 
portions of iron and tin, and to these latter its peculiar properties are attributed. 
It has a brass yellow colour, is close in grain, is free from porosity, and has considerable hardness, 
whereby it is well adapted for bearing-metal, or other purposes where resistance to friction is needed. 
Sterro-metal possesses another quality which, in reference to its application for guns, is regarded 
as more important than its high tenacity, namely,—great elasticity. 
The inventor proposes that in heavy ordnance the interior should consist of a tube of sterro- 
metal, and over this wrought or cast-iron should be shrunk from the breech to beyond the 
trunnions.—(See an interesting letter in the “Times” of 3rd February, 1863). 
