996 Transactions of the A yf eric an Institute. 



Experiments have sliown Sir AVilliam Armstrong correct in Iiis state- 

 ment tliat in hard well tempered steel shot the work expended on the 

 shot was one-tenth of the whole work ; with soft steel the work 

 expended on the shot was two-tenths, and with soft iron five-tenths. 

 This he explains by the dynamic effect of heat at the instant of con- 

 cussion. The experiments on the English armor targets show that 

 loose wood backing is useless, and a rigid backing of w'ood is an 

 advantage, and is very great if it has an iron skin behind, connected 

 by ribs with the front plate. 



Concrete Beidges. 



The new concrete structures recently erected on the Metropolitan 

 Extension railway, between Paddington and Brompton, London, 

 has been tested to ascertain its tensile strength. The structure is an 

 arch entirely of concrete, of seventy-five feet span, and only seven 

 feet six inches rise. It is three feet six inches deep at the crown, and 

 has a uniform width of twelve feet. The materials and proportions 

 employed were six of gravel to one of Portland cement, and depend- 

 ence for cohesion was placed rather upon thoroughly mixing the 

 materials than ramming. In making the test, 170 tons in weight 

 were equally distributed over the surface, and a train of several 

 freight cars, weighing fifty tons, passed over it. Under this weight 

 there was practically no deflection. It seems probable that this 

 favorable result wall lead to the more extensive use of this artificial 

 •mixture as a building material. 



Glass-avool. 



At the last exhibition by the Pol3'technic Association of Vienna, 

 a newproduct of art was shown, consisting of glass spinnings, and embra- 

 cing ornaments for the hair, ribbons, bracelets, cufis, collar?;;, Avatcli- 

 chains, imitations of curled and smooth ostrich feathers, etc. They 

 were manufactured by M. Jules de Brunfaut, in Pai-is, and difi'er 

 from the articles of this kind hitherto produced, in being much finer, 

 more tenacious, flexible, and durable. Some of the glass-wool is said 

 to be as fine as a spider's web, and so flexible that it may be used as 

 thread. 



Preparation of Oxygen from Sulphukig Acid. 

 The process of Messrs. Clomadena and Mcret consists in ira])regna- 

 ting pieces of pumice stone with sulpliuric acid, rind afterward expo- 



