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ELECTRIC LAUNCH.

Trials have been made at Havre with an electric launch built to the order of the French government by the Forges et Chantiers de la Mediterranee.  The vessel, which has rather full lines, measures 28 ft. between perpendiculars and 9 ft. beam, and is 5 tons register.

The electromotor is the invention of Captain Krebs, who is already well known on account of his experiments in connection with navigable balloons, and of M. De Zede, naval architect.  The propeller shaft is not directly coupled with the spindle of the motor, but is geared to it by spur wheels in the ratio of 1 to 3, in order to allow of the employment of a light high-speed motor.  The latter makes 850 revolutions per minute, and develops 12 horse power when driving the screw at 280 revolutions.  Current is supplied by a new type of accumulators made by Messrs. Commelin & Desmazures.  One hundred and thirty two of these accumulators are fitted in the bottom of the boat, the total weight being about 2 tons.

In ordering this boat the French government stipulated a speed of 6 knots to be maintained during three hours with an expenditure of 10 horse power.  The result of the trials gave a speed of 61/2 knots during five hours with 12 horse power, and sufficient charge was left in the accumulators to allow the boat to travel on the following day for four hours.  This performance is exceedingly good, since it shows that one horse power hour has been obtained with less than 60 lb. of total weight of battery.

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THE COMMERCIAL EXCHANGE, PARIS.

Leveling the ground, pulling down old buildings, and distributing light and air through her wide streets, Paris is slowly and continuously pursuing her transformation.  At this moment it is an entire district, and not one of the least curious ones, that is disappearing, leaving no other trace of its existence than the circular walls that once inclosed the wheat market.

It is this building that, metamorphosed, is to become the Commercial Exchange that has been so earnestly demanded since 1880 by the commerce of Paris.  The question, which was simple in the first place, and consisted in the conversion of the wheat market into a commercial exchange, became complicated by a project of enlarging the markets.  It therefore became necessary to take possession, on the one hand, of sixty seven estates, of a total area of 116,715 square feet, to clear the exchange, and, on the other, of 49,965 square feet to clear the central markets.  In other words, out of $5,000,000 voted by the common council for this work, $2,800,000 are devoted to the dispossessions necessitated by the new exchange, $1,800,000 to those necessitated by the markets, and $400,000 are appropriated to the wheat market.