Lieut.-Colonel A. Strange on Aluminium Bronze. 513 



" It appears from these experiments, and from the concurrent 

 testimony of those who have given it a fair trial, that the 10 per 

 cent, aluminium bronze is far superior, not in one or some, but 

 in every respect, to any metal hitherto used for the construction 

 of philosophical apparatus, and that for such purposes it may be 

 employed in the dimensions that would be proper in the case of 

 cast steel. All parts which otherwise would be made of steel 

 may with perfect safety, andj even with advantage, be made of 

 the new alloy, particularly such parts as bolts, and fixing, tangent, 

 and micrometer screws. Its hardness and comparative inoxidiza- 

 bility point it out as peculiarly adapted for pivots, axes, and 

 bearings. If employed for receiving the graduation of circles, 

 the necessity for inlaying another metal will be obviated, by 

 which two advantages will be gained : the hammering which 

 forms part of the operation of inlaying, and which, more or less, 

 must cause unequal density and tension in the circle subjected 

 to such treatment, will be dispensed with ; and the effect of in- 

 equality of expansion in the circle and the inlaid strip will no 

 longer be a cause of apprehension. With respect to the due 

 visibility of divisions cut on this metal, opinions will perhaps 

 differ. I can only say that I should be well content to observe 

 with them. 



" The use of this alloy for the construction of the new Great 

 Theodolite is, in the opinion of Messrs. Simms, and in my own, 

 fully justified by what we now know of it ; and the effect of 

 using it will be to keep the weight of the instrument within 

 reasonable limits, notwithstanding its possession of means and 

 appliances not hitherto bestowed on such instruments. 



" Two points remain — the making of the alloy, and its cost. 

 " The metal aluminium is at present extracted in England by 

 one firm only, Messrs. Bell Brothers, Newcastle, under a license 

 from M. Deville, the French discoverer of the process. I have 

 met with instances of failure in making the alloy with copper. 

 Two main points only, however, seem to require particular atten- 

 ' tion. First, extremely pure copper must be used. The best is 

 copper deposited by electricity ; but that kind is very expensive ; 

 the next best is copper from Lake Superior, which makes an 

 alloy of excellent quality. The ordinary coppers of commerce 

 generally fail, owing, it is said, chiefly to the presence of iron, 

 which appears to be specially prejudicial. The second precaution 

 is to re-melt the alloy two or three times. The first melting of 

 10 aluminium and 90 copper produces an alloy of excessive brit- 

 tleness. Each successive melting, up to a certain point deter- 

 mined by the working-, and particularly the forging-properties 

 of the metal, improves its tenacity and strength. It is probable 

 that after several meltings there will remain in combination with 

 Phil. Mag. S. 4. No. 164. Suppl. Vol. 24. 2 M 



