MECHANICS AND USEFUL ARTS. 81 



mixed and welded in the air-furnace, drawn down into rolls, and re- 

 fagoted; these are subsequently drawn down, and are then ready 

 for being made into gun-barrels, either with or without spirally twist- 

 ing them ; to form Damascene barrels from this is perfectly safe. 

 The manufacture of swords is another article to which this improve- 

 ment is applied. All Mr. Greener's investigations tend to satisfy him 

 that it is in this way that the Arabs produce their finely-tempered 

 Damascus swords; namely, using two steels of different carboniza- 

 tion, mixing them in the most intimate manner, and twisting them 

 many fantastic ways, but preserving method in their fancy. Temper- 

 ing by crystallizing the steel, as is ordinarily done, is far from the 

 wisest way. The Damascus blade in its fibrous state, or hammer- 

 hardened, is more difficult to break, by 100 per cent., than the best 

 English-made blade. Temper it in the same way, however, and it 

 shows no greater tenacity than our own. From these and other 

 facts, the conclusion may be drawn, that swords constructed of dis- 

 similar steel, tempered by condensation of its fibres, either by repeated 

 rollings, hammerings, or in any other way, are the best. Athenaum, for 

 September. 



CHAIN-LINKS FOR CABLES, ETC. 



SOME experiments have recently been made with a view of testing 

 the power of links for inooring-chains, cables, and other purposes, 

 formed on the principle of Mr. Price, a gentleman already known 

 among scientific men as the inventor of improvements in anchors. 

 The object of the inventor is to lessen the expense and weight of 

 chains as at present constructed, by doing away the stud or crossbar 

 of the link, and making the link with straight or parallel sides, and 

 not of the present oval shape; his principle being that, the fibre of 

 the iron being kept straight, it will sustain or resist a much greater 

 weight, or strain, than when force is exerted against it transversely. 

 The test was completely satisfactory ; a link of iron, seven eighths of an 

 inch in diameter, with parallel sides, 3 inches in length, and 2 in 

 breadth, without a stud, not breaking till a strain of 18 tons was put on 

 it, being S tons beyond the government proof. London Paper. 



THE POWER OF IRON TO RESIST COMPRESSION AND EXTENSION. 



WHILE making his plans and estimates for the Britannia Tubular 

 Bridge over the Menai Straits, Mr. Stephenson, the engineer, caused 

 several trials to be made in order to ascertain some facts which were 

 deemed important. These are well described by a writer in a late num- 

 ber of the London Quarterly, from which we make considerable extracts, 

 as the results are new and of great importance. 



" One of the most interesting and important results of the prelimi- 

 nary investigations so ably conducted by Mr. Fairbairn and Mr. Hodg- 

 kinson, was the astonishing difference found to exist between the 

 power of cast and that of wrought iron to resist compression and ex- 

 tension. From the experience which engineers and builders had ob- 



