20 ANNUAL OF SCIENTIFIC DISCOVERY. 



give a more familiar idea of the invention, three penny pieces, 

 mounted on an axis, with a little distance between them, form, to all 

 intents and purposes, the disc-propeller. It seenis strange that a pad- 

 dle-wheel without paddles should be able to propel at all ; but Mr. 

 Ashton has proved that not only does it propel, but that it propels 

 nearly, if not altogether, as quickly as if floats were attached. It 

 was claimed, moreover, to be much more economical than a paddle, 

 driving, with a given speed, the vessel with a smaller consumption or 

 coal ; producing no vibration ; and, what is of no small importance in 

 canal navigation, not the slightest swell. 



Iron Fabrication. In illustrations of iron fabrications the Exhibi- 

 tion was exceedingly rich. The Butterley Iron Company, of Eng- 

 land, exhibited a rolled boiler-plate twelve feet nine inches long, 

 seven feet six inches wide, and one and a half inch thick. Krupp, 

 the celebrated steel manufacturer, of Essen, Germany, has recently 

 proposed to construct rolls not less than seventeen feet in width, and 

 to manufacture therewith a boiler-plate sufficiently large to form of 

 itself an entire boiler ; and from the great success which Mr. Krupp 

 has already achieved in working iron, there can be little doubt but 

 that he will eventually accomplish his object. 



Of sheet-iron there were numerous fine illustrations. Fine sheets 

 from Belgium were especially characterized by a smooth and dark- 

 bluish-gray, glossy surface. The color here was obviously due to a 

 thin and firmly adherent skin of oxide of iron, which has been de- 

 tached here and there near the edges of several of the sheets, clearly 

 revealing the color of the subjacent iron. The London Times, in 

 noticing these specimens, stated that they could not as yet be pro- 

 duced in England. Russia, however, still continues without a com- 

 petitor in the production of a peculiar description of sheet-iron, 

 which has long been highly esteemed in commerce. The quality of 

 the iron, which is both smelted and worked with charcoal throughout, 

 is excellent, and the dark polish on the surface is remarkable. The 

 process of manufacture is not known, and mythical stories are cur- 

 rent as to the precautions taken with a view to secrecy, and the 

 lamentable fate of those who have gained unlawful access to the 

 works in order to possess themselves of the mystery. The manufac- 

 ture of this description of sheet-iron in other parts of the world is a 

 great desideratum, and the man who succeeds in introducing it will 

 probably not have cause to repent. The Russians are said to anneal 

 their sheets with charcoal-dust interposed, and finally to hammer them 

 in packets. They are not all obtained equally good, and a selection 

 is accordingly made. 



No metallurgical illustrations in the Exhibition were more inter- 

 esting at the present time than the rolled armor-plates for ships. We 

 give the dimensions of two manufactured by the Atlas Works of Shef- 

 field : (No. 1.) Length 21 feet 8 inches, width 4 feet 2 inches, 

 thickness 6| inches, weight 10 tons 12 cwt. (No. 2.) Length 24 

 feet, width 3 feet 8 inches, thickness 5 inches, weight 7 tons 1 7 cwt. 

 A few years ago the rolling of such enormous masses of iron would 

 have seemed incredible. In the Great Exhibition of 1851, Messrs. 

 Bagnall, of South Staffordshire, England, presented a rolled round 

 bar, which was considered extraordinary on account of its size, but 



