682 ANNUAL RECORD OF SCIENCE AND INDUSTRY. 



fine piece of engineering. The valley is narrow, the river-bed 

 is composed of mud and sand to the depth of 50 to 180 feet, 

 and the river is subject to great and rapid freshets, which 

 sometimes raise the surface forty feet in twenty-four hours. 

 On these and other accounts it was decided to be impossible 

 to attempt to locate a pier in the river, and it was therefore 

 spanned by a single iron arch of 525 feet spring, or a little 

 larger than the central span of the great St. Louis Bridge. 

 The arch abuts against piers of masonry on each bank. The 

 mounting of the arch presented great difficulties, but was ac- 

 complished by the help of steel cables. The two halves met 

 at the key with great precision. 



AN UNDERGROUND RAILWAY FOR PARIS 



is proposed, and if report may be credited, the following plans 

 have met with approval. The central station will be located 

 at the Gardens of the Palais Royal, from which three lines 

 will radiate: one to the Exchange, the Opera, the railway 

 station of St. Lazare, thence to the Bategnolles, communi- 

 cating with the Great Western Railway and the Chemin de 

 Fer de Ceinture; a second to Les Halles, the Boulevard Se- 

 bastopol, Boulevard de Strasbourg, the Great Eastern and 

 Great Northern Railways (from the Boulevard de Strasbourg 

 a branch line would lead to the Vincennes and Lyons Rail- 

 way stations, passing beneath the Seine to the left side of 

 the river) ; and a third to the Rue de Rennes, the Mont Par- 

 nasse Railway stations, and the station for Sceaux and Gen- 

 till v. The cost of this underground net-work is estimated at 

 $30,000,000, and, according to statement, will be borne joint- 

 ly by the state, the Department of the Seine, aud the munici- 

 pality. 



STEAM-HEATING FOR CITIES AND TOWNS. 



The experiment of heating the city of Lockport, X. Y., with 

 steam, by what is now generally called the Holly system, is 

 believed to have criven general satisfaction. Some five miles 

 of mains and laterals, protected by a non-conducting envel- 

 ope, were in use during the last winter. The system has 

 lately been introduced into Springfield, Mass., and its trial in 

 several other localities is spoken of. 



