512 Lieut. -Colonel A. Strange on Aluminium Bronze 



r> v 



" (8) Resistance to atmospheric influences. — Messrs. Simms 

 state, ' it does not readily tarnish/ This, likewise, is entirely a 

 relative question. Absolute inoxidizability, however desirable, 

 is hardly to be expected. Suffice it that the new alloy tarnishes 

 much less readily than any metal usually employed for astrono- 

 mical instruments, viz., gun-metal, brass, silver, cast iron, or 

 steel. 



" (9) Fitness to receive graduation. — Messrs. Simms state, 

 ( Aluminium bronze takes a fine division, and it will not be 

 necessary to inlay another metal, as is usually done, to receive 

 the graduation.'' This opinion is fully justified by the specimen 

 of graduation executed by Messrs. Simms, the lines of which are 

 remarkably pure and equable, characteristics never presented, in 

 the same degree, they inform me, by lines cut on any other cast 

 metal. May not this superiority indicate that the alloy in ques- 

 tion is peculiarly homogeneous ? The lines are very distinct 

 under the microscope, notwithstanding the yellow colour of the 

 metal. 



" (10) Elasticity. — I possess no direct experiments bearing 

 on this point. But that the alloy has considerable elasticity is 

 unquestionable. I may here state that an eminent Parisian 

 instrument-maker informed me that, of all the wires tried for 

 the suspension of Foucault's pendulum for illustrating the rota- 

 tion of the earth, none, not even those of steel, were so durable 

 under that severe ordeal as wires made of aluminium bronze. 

 It would appear, therefore, to be the most proper material for 

 the suspension springs of clock pendulums. 



"(11) Fitness for being made into tubes. — It admits of every 

 process necessary for this purpose. It can be soldered with 

 either silver or brass solder ; it can be rolled into sheet metal ; 

 and it can be hammered and drawn. Hitherto telescope tubes, 

 the cones of transit axes, the pillars of altazimuths, &c, have 

 been made almost exclusively of yellow brass, a metal very defi- 

 cient in rigidity. Gun-metal does not admit of being rolled, 

 and has therefore never been used for the tubular parts of instru- ' 

 ments, for which the new alloy seems pre-eminently suitable. 



" (12) Specific gravity. — The specific gravities of alloys of 

 aluminium and copper, as determined by Messrs. Bell, are 



3 per cent, of aluminium . . . 8*691 



4 „ „ ... 8-621 



5 „ ... 8-369 

 10 „ ... 7-689 



The last named, which is the best for the purposes now under 

 notice, is very nearly the same as that of wrought iron, and less 

 than that of either brass or gun-metal. 



