Lieut. -Colonel A. Strange on Aluminium Bronze. 511 



under compression is so different, cast iron yielding suddenly 

 and almost totally, and the new alloy more gradually and par- 

 tially. Astronomical instruments, however, are more dependent 

 on the rigidity or resistance to a transverse force than to any 

 other ^quality. 



" (3) Malleability. — Mr. Anderson states on this head : — 



"'The qualities of this metal for forging-purposes would 

 appear to be excellent ; with the exception of the part heated 

 to a red heat in the shade, all show that it is a good workable 

 material under the hammer almost up to melting-point.'' 



"I may add that there were specimens in the Exhibition, 

 showing that the alloy could be drawn out under the hammer 

 almost to a needle point. 



" I come now to the experiments tried by Messrs, Simms. 



" (4) Transverse strength. — As the absolute determination of 

 the force necessary to break or permanently bend a bar of metal 

 was beyond our appliances, I begged Messrs. Simms to be satis- 

 fied with a comparative value of the rigidity of the new alloy ; 

 that is, to ascertain the relative resistances of gun-metal, brass, 

 and aluminium bronze, to a force insufficient to produce per- 

 manent flexure. This they succeeded in doing, and report as 

 follows : — 



" e The same weight applied to three bars altered the index of 

 our instrument as under : 



Brass 2*22 divisions. 



Gun-metal .... 0'15 „ 

 Aluminium bronze . . 0*05 „ ' 



" Hence aluminium bronze would appear to be 3 times more 

 rigid than gun-metal, and upwards of 44 times more rigid than 

 brass. 



ft (5) Expansive ratio. — This determination was also a com- 

 parative one. Messrs. Simms found that c aluminium bronze 

 is less affected by change of temperature than either gun-metal 

 or brass (a little less than gun-metal, and much less than 

 brass).'' 



" (6) Founding -qualities. — Regarding this there is ample ex- 

 perience. The alloy produces admirable castings of any size. 



" (7) Behaviour under files, cutting -tools, fyc. — In this respect, 

 also, it leaves nothing to be desired. It does not clog the file ; 

 and in the lathe and planing-machine the tool removes long- 

 elastic shavings, leaving a fine bright, smooth surface. Messrs. 

 Simms state, — 



" ' It can be worked with much less difficulty than steel, and 

 we should think that screws made of it would (notwithstanding 

 the original great cost of the metal) prove in the end less expen- 

 sive than screws made of steel/ 



