forms an indent in what would otherwise be a straight line on the paper.  The distance pen, by a similar arrangement, traces another line on the cylinder in which are indents corresponding to fixed distances of travel along the tank, the indents being caused by small projections which strike a trigger at the bottom of the carriage as it passes, and make electric contact.  From these time and distance diagrams accurate account can be taken of the speed at which the model and its supporting carriage have been driven.  Thus on the same cylinder is recorded graphically the speed and resistance of the model.  The carriage may be driven at any assigned speed by adjusting the governor of the driving engine already alluded to, but the record of the speed by means of the time and distance diagrams is more definite.  When the resistances of the model have been obtained at several speeds, varying in some cases from 50 to 1,000 feet per minute, the speeds are set off in suitable units along a base line, and for every speed at which resistance is measured, the resistance is set off to scale as an ordinate value at those speeds.  A line passing through these spots forms the “curve of resistance,” from which the resistance experienced by the model at the given trial speeds or any intermediate speed can be ascertained.  The resistance being known, the power required to overcome resistance and drive the actual ship at any given speed is easily deduced by applying the rule before described as the law of comparison.—­The Steamship.

* * * * *

THE SHIP IN THE NEW FRENCH BALLET OF THE “TEMPEST.”

A new ballet, entitled the “Tempest,” by Messrs. Barbier and Thomas, has recently been put upon the stage of the Opera at Paris with superb settings.  One of the most important of the several tableaux exhibited is the last one of the third act, in which appears a vessel of unusual dimensions for the stage, and which leaves far behind it the celebrated ships of the “Corsaire” and “L’Africaine.”  This vessel, starting from the back of the stage, advances majestically, describes a wide circle, and stops in front of the prompter’s box.

[Illustration:  FIG. 1.—­SHIP OF THE “TEMPEST,” IN PROCESS OF CONSTRUCTION.]

[Illustration:  FIG. 2.—­SETTING OF THE SCENERY BEFORE AND AFTER THE APPEARANCE OF THE SHIP.]

As the structure of this vessel and the mechanism by which it is moved are a little out of the ordinary, we shall give some details in regard to them.  First, the sea is represented by four parallel strips of water, each formed of a vertical wooden frame entirely free in its movements (Fig. 2).  The ship (Figs. 1, 2, 3, 4 and 5) is carried by wheels that roll over the floor of the stage.  It is guided in its motion by two grooved bronze wheels and by a rail formed of a simple reversed T-iron which is fixed to the floor by bolts.  In measure as it advances, the strips