Polytechnic Association Proceedings. 671 



pered and forged; further, it is possible to make pieces of large 

 dimensions. 



USE OF DISTILLED WATER. 



The Pacific coast of South America, between the 18th and 28th 

 parallels of south latitude, is a rainless region. All the seaport 

 towns, for a distance of six hundred miles, are supplied with fresh 

 water for drinking and cooking purposes, from sea-water, which is 

 mostly distilled by means of imported coal. Not only cattle, but 

 locomotives and stationary steam-engines are supplied with distilled 

 water. The few natural springs, within from thirty to fifty miles 

 of the ocean, contain so much saline matter as to be rendered unfit 

 for quenching thirst. 



GIGANTIC GLASS PLATES. 



The French Glass Company, owning the factories at St. Gobain 

 and Chauuy, which were fii'st erected 1693, exhibit at the Paris 

 Exposition some of the finest specimens of plate glass. One plate 

 glass, unsilvered, measures 5.93 by 3.64 meters, or nearly twenty 

 by twelve feet. One silvered mirror is a trifle larger in surface, 

 being 5.90 by 3.68 meters. The glass for these and several other 

 plates was melted in a single pot capable of holding a ton of the 

 fused material. Silvering very large plates of glass is a delicate 

 operation. The sheet tin for each square meter weighs two pounds; 

 if less quantity is used, the mercury is dissolved before the operar 

 tion is completed. 



PNEUSIATIC DISPATCH. 



The plan of carrying packages through a tube, by means of com- 

 pressing or exhausting the air within it, fii'st proposed and tried on 

 a small scale by Richai'dson, of Boston, has been in successful ope- 

 ration for several years in London. The London Engineering 

 describes an apparatus of much cheaper construction, consisting 

 of leaden tubes, protected externally by split pipes of wrought 

 iron, through which written messages are sent from place to place 

 in little carriers of gutta percha. The suction or pressure required 

 is developed in reservoirs by means of a small steam-engine and 

 air-pump. Forty messages can be sent in each carrier, and twelve 

 carriers can be dispatched every five minutes. Messrs. Leemans & 

 Hulske, of Berlin, and Mignon & Rouart, of Paris, have exhibited 

 similar plans. The latter-named gentlemen propose to use iron 

 pipes glazed on the inside. 



