24 ANNUAL OF SCIENTIFIC DISCOVERY. 



preventing it from rising in the mould. The action of chemical agents 

 upon it is also weakened, and the copper gains in hardness and tena- 

 city without losing its malleability, thus producing an alloy which has 

 the malleability of brass, with the hardness of bronze. 



Aluminum bronze has been selected by Col. Strange as the most ap- 

 propriate metal for the construction of the large theodolite for the use 

 of the Trigonometrical Survey of India. The horizontal circle of this 

 theodolite, is three feet in diameter, and the effect of using this alloy 

 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. In the manufacture of the alloy, Col. 

 Strange says that extremely pure copper must be used; electrotype 

 copper is best, and Lake Superior copper stands next, giving an alloy 

 of excellent quality. The ordinary coppers of commerce generally 

 fail, owing, it is said, to the presence of iron, which appears to be spe- 

 cially prejudicial. Further, the alloy must be melted two or three 

 times, as that obtained from the first melting is excessively brittle. 

 " Each successive melting, up to a certain point, determined by the 

 working, and particularly the forging properties of the metal, improves 

 its tenacity and strength." The present price of English-made 10 per 

 cent, aluminum bronze is 6 shillings 6 pence per Ib. This is four or 

 five times that of gun-metal. 



MALLEABLE IRON NAILS. 



There is a description of nails of cast malleable iron coming into use 

 for fixing slates on to the roofs of factories and similar buildings. They 

 oxidize much less in damp air than common iron nails, or even copper 

 ones. To manufacture them, very hot metal is run into ordinary sand 

 moulds. These malleable iron nails are very brittle before being placed 

 in the annealing furnace. Their sojourn in the furnace renders them 

 very ductile. They are then put into polishing barrels, in which they 

 are cleaned, whereupon they are thrown into a zinc bath to obtain 

 a coating. London Mechanics' Magazine. 



IMPROVEMENT IN STEEL WORKING. 



Mr. Anderson, Assistant Superintendent of Woolwich Arsenal, an- 

 nounces the discovery of a simple process by which steel is rendered as 

 tough as wrought-iron without losing its hardness. This change is ef- 

 fected in a few minutes by heating the metal and plunging it in oil, 

 after which the steel can be bent, but scarcely broken. The value of 

 this discovery will be at once appreciated by those who are aware of 

 the difficulties hitherto experienced in obtaining a suitable material for 

 the interior tubes of built-up guns. 



FILES MADE BY MACHINERY. 



The manufacture of files by machinery is said to have been success- 

 fully commenced in Birmingham, England. The blanks are forged by 

 machinery, and they are then cut with the French machine of M. Ber- 

 not. The machine, which is very compact, resembles a small steam- 

 hammer in its general appearance. It is provided with a vertical slide, 

 carrying a chisel on the lower end. The top of this slide is pressed by 

 a flat spring, which is governed by a cam mounted upon a shaft, and 



