X. NAVAL ENGINEERING.--The Empress of India.--The pioneer of a fast mail service to ply in connection with the Canadian Pacific Railway between Vancouver, China, and Japan.--1 illustration XI. PHYSICS.--Stereoscopic Projections.--A most curious method of securing stereoscopic effects with the magic lantern upon the screen, involving the use of colored spectacles by the spectators. --1 illustration XII. TECHNOLOGY.--Gaseous Illuminants.--By Prof. VIVIAN B. LEWES.--The fifth and last of Prof. Lewes' Society of Arts lectures, concluding his review of the subject of gas manufacture * * * * * THE NEW LABOR EXCHANGE AT PARIS. There will soon be inaugurated (probably about the 14th of July) a new establishment that has long been demanded by the laboring population, that is to say, a new labor exchange, the buildings of which, situated on Chateau d'Eau Street, are to succeed the provisional exchange installed in the vicinity of Le Louvre Street. The new structures have been erected from plans by Mr. Bouvard, and occupy an area of seventeen hundred meters. The main work is now entirely terminated, but the interior decorations are not yet completely finished. The distribution comprises a vast meeting room, committee rooms for the various syndicates, offices in which the workmen of the various bodies of trades will find information and advice, and will be enabled to be put in relation with employers without passing through the more or less recommendable agencies to which they have hitherto been obliged to have recourse. [Illustration: NEW LABOR EXCHANGE, PARIS.] Upon the whole, the institution, if wisely conducted, is capable of bearing fruit and ought to do so, and the laboring population of Paris should be grateful to the municipal council for the six million francs that our ediles have so generously voted for making this interesting work a success. On seeing the precautions, perhaps necessary, that the laborer now takes against the capitalist, we cannot help instituting a comparison with the antique and solid organization of labor that formerly governed the trades unions. Each corporation possessed a syndic charged with watching over the management of affairs, and over the receipts and the use of the common resources. These syndics were appointed for two years, and had to make annually, at least, four visits to all the masters, in order to learn how the laborers were treated and paid, and how loyally the regulations of the corporation were observed. They rendered an account of this to the first assembly of the community and cited all the masters in fault.