MECHANICS AND USEFUL ARTS. 99 



the arms were found loaded with Johnson & Dow's cartridges ; many 

 of these cartridges were about half way down in the barrels of the 

 pins, and in many cases the ball end of the cartridge had been put 

 into tlu'. gun first. These cartridges were found mostly in the Enfield 

 rifle-musket. This statement constitutes one of the strongest of argu- 

 ments in favor of a change to breech-loading guns. With brecch- 

 loadi'rs it \voiild be impossible to get in more than one charge at a time, 

 and a man could tell at a glance whether his piece was discharged or not. 



NEW GUN METAL. 



A writer in the London Times gives some interesting particulars of 

 a new gun metal lately invented in Austria by Baron von Rosthorn. 

 In-fore giving any account of this new alloy, the writer states his 

 opinion that the days of wrought iron are numbered, and that its 

 place will be soon supplied by steel in some form or other. The new 

 alloy, whu-h has received the name of "sterrometal," from a Greek 

 word signifying tough or firm, is composed of copper, spelter, iron, 

 and tin, in proportions that may be slightly varied without much 

 affecting the result. In color it resembles brass rather than gun metal ; 

 it is very close in its grain and free from porosity. It is possessed of 

 considerable hardness, and will take a very fine polish. Several emi- 

 nent Vienna engineers have tried it for the cylinders of hydraulic 

 presses with great success. Two specimens of the alloy have been 

 submitted to rigorous tests by the Polytechnic Institute, of Vienna and 

 the Imperial Arsenal. The proportions used in each case were the 

 following : 



Polytechnic Institution. Imperial Arsenal. 



Copper 55-01 57 -(53 



Spelter 4->-:;<> 40-22 



Iron 1-77 1'SG 



Tiu 0-8:J 0.15 



100-000 99. SO 



The specimen tested at the Polytechnic Institute gave the following 

 results per sectional inch (English) : A bar prepared by simple fusion 

 bore a weight of 27 tons. Forged red-hot it broke at 34 tons. Drawn 

 cold, at 38 tons : the figures in the case of the specimen tried at the 

 Imperial Arsenal being 28, 32, and 37 tons respectively ; while the 

 best English gun metal, containing ten per cent of tin and 90 per cent 

 of copper, broke at 18 tons under similar circumstances. The spe- 

 cific gravity of the metal is about 8'37 when forged hot. 



These results, which are official, are truly astounding when we con- 

 sider that the average breaking strain of wrought iron, as given by 

 Mr. Anderson, of Woolwich Arsenal, is only 26 tuns. The elasticity 

 of the sterrometal is also very great. It may be stretched g-^ of 

 its length without undergoing permanent elongation ; gun metal giving 

 only yrVo"' an( l wrought iron y'sV o 1 - -^ SLir P r i se i s > therefore, felt 

 when we are told that a tube of sterrometal is capable of resisting 

 a pressure of 763 atmospheres, a tube of wrought iron of similar size 

 and form giving way under 267. 



New Principle in (runnery. The following description of an 

 alleged new principle in Gunnery, devised by Mr. James Mackay of 

 Liverpool, is copied from English journals : 



