It is by the swing of the H. R. pendulum when the torpedo is diving or ascending, and by the motion of the piston when the torpedo is above or below the set depth, that the position of the angle guide is determined, which thereupon transmits, by means of the impulsive movement, the proper throw to the H. R.

Movement of the piston will tip the angle guide, so also will movement of the H. R. pendulum, and the latter dominates the force exerted by the piston, as will be seen later on.

The mechanism of the impulse movements consists of two racks TT (see Fig. 2) sliding in a frame with reciprocal motion simultaneously approaching each other and receding. The motion is derived from two eccentrics which themselves take motion through gearings from worms on both shafts. These impulses are very rapid, usually 41⁄2 per second; the number depending, of course, upon the speed of the shaft, and are continuous as long as the shaft revolves.

These movements or impulses act upon the rudder in this way : The tiller rods have attached to them the little arms or "pallets," PP (Fig. 2). These pallets are pivoted at the center. On one

h

FIG. 2.

end is a pin upon which rest the light springs of the "angle guide."

When the angle guide is tipped by the motion of either the piston or H. R. pendulum, or both, acting together or against each other, the pallet will also be tipped and the toe of the pallet coming in the path of the rapidly moving impulse rack will engage the teeth on the rack, and thus the tiller rod be pushed either forward or to the rear, transmitting motion to the horizontal or diving rudder. In a similar way the V. R. pendulum actuates an adjustable V. R. angle guide, to control the V. R. pallet in reference to the upper impulse racks.

It is clear that as long as the torpedo is moving at set depth with its horizontal axis in the plane of the horizon, the pallets also will be in the same plane, and the impulse racks will travel to and fro without coming into contact with them. There will be no move of either piston or pendulum.

Suppose, however, the torpedo is above the set depth. The pressure on piston being less than spring tension, the piston will be set out, the angle guide will tip and engage the forward end of the pallet with the impulse rack, and produce a certain amount of down rudder, causing the torpedo to dive. The pendulum then swings forward, and in doing so tips the angle guide in the opposite direction, which engages the after end of the pallet in the impulse rack, causing up rudder, thus checking the dive. The pendulum's influence being thus greater than that of the piston, this result is obtained, otherwise the torpedo would continue to dive. If the torpedo is below set depth and approaching it, the reverse action takes place.

IV. The “immobilizer" is a rod which has longitudinal motion given by the pitch frame. It holds the pendulum forward or back as desired (when the torpedo is launched) a short interval of time, about two or three seconds perhaps. It will be seen that by holding the H. R. pendulum forward, the angle guide will tip the after end of the pallet to engage the impulse rack, thus producing up rudder. In this way the torpedo's dive is checked. The H. R. pendulum is automatically released at the set time.

V. The torpedo is ejected from the tube (above water) by a 5 to 6-oz. charge of black powder, this being sufficient to throw the torpedo clear of the ship's side.

VI. The fly wheel is spun up by means of a small steam motor which is readily disconnected from the torpedo. The energy in the wheel at 10,000 revolutions per minute is equal to 500,000 ft. pounds, and it requires 30 horse power for one minute to store it, but it requires only 4 H. P. to keep the wheel at 10,000 after it has been spun up.

The range of the torpedo is 800 yards; its speed over 400 yards 26 knots. This is the maximum yet attained with the torpedo of 14.2 inches diameter.

[COPYRIGHTED.]

U. S. NAVAL INSTITUTE, ANNAPOLIS, MD.

MARCH 21, 1895.

LIEUTENANT COMMANDER B. F. TILLEY, U. S. Navy, in the chair.

THE SOLAROMETER; A MODERN NAVIGATING
INSTRUMENT.

By LIEUTENANT W. H. BEEHLER, U. S. Navy.

The great progress that has been made in naval architecture and marine steam engineering demands improvement in the instruments for navigating the magnificent products of human ingenuity as exemplified in the modern men-of-war.

The solarometer claims to meet this demand by providing a method of making astronomical observations independent of the visibility of the sea horizon.

The primary object of the solarometer is this feature of its artificial horizon, which is so combined with the astronomical values of declination, hour angle, azimuth and altitude in relation to the observer's latitude and zenith that all the elements of the nautical astronomical problems are solved.

The mechanical solution of the problem as in the solarometer becomes more of a practical necessity as a result of hourly opportunities to astronomically determine the ship's position and compass errors; not because of any defects in the mathematical computations from altitude by the sextant, but in order to save the time these calculations involve.

If observations were taken once or twice every hour, they would involve a total of from six to eight hours daily work with sextant, alidades and logarithms to obtain the results of those observa

tions, and this total time would be so distributed throughout the 24 hours that there would be very few spare minutes left for the navigator to do anything else than observe and calculate the results of his observations.

The solarometer obviates elaborate logarithmic calculations and combines in itself a pelorus; so that it furnishes a complete solution of the entire problem to ascertain ship's position and compass errors in the space of time ordinarily required to observe the altitude by the sextant and take its bearing with a pelorus.

The general principles upon which the solarometer is constructed may be concisely stated to consist of a series of circles representing the nautical astronomical triangle supported upon a constant level base which locates the position of the observer's zenith in that triangle.

There is a definite relation between all the five quantities of declination, latitude, hour angle, altitude, and azimuth, such that with each and every variation of the value of one or more of these quantities, the others have corresponding values. The variations of all these quantities cause an infinite variety of possible values to the astronomical triangle, and all are beautifully illustrated by the solarometer.

The Nautical Almanac gives the right ascension and declination of a heavenly body on a circle which passes through the poles. The book of azimuth tables for the same time and place gives the position of the same body or a circle which passes through the observer's zenith. These two publications give the exact position of the same body on two different circles for the same time and place. If the body is on two circles at the same time it must be at their intersection, and if a telescope be fixed at this intersection of the circles representing those of the astronomical triangle, it follows that a body cannot be seen in the axis of that telescope without making this system of circles show the hour angle, elevation of the pole and azimuth, or the observer's longitude, latitude and the ship's compass errors.

This is not a new principle in astronomy but merely a novel point of view, involving a mechanical movement in unison of two variable systems of coordinates, viz. declination and hour angle, with latitude and azimuth, having their junction marked by the body's zenith distance or altitude. The axis of the telescope lies in the