"As it appeared quite clear that the run was not made in the direction intended, and that about one mile must have been covered from the start, ten minutes having already passed, the boat was brought to the surface of the water just in time to prevent her from running on rocks that lay about twenty yards straight ahead and sixty yards down from the starting point.

"The boat had been started to run over one mile up stream, and the mile-run ended sixty yards down stream, with the boat heading exactly opposite to her original direction. This erratic action of the compass was discovered to be due to heeling, or inclining from the horizontal position, and that it could not be corrected in that boat on account of the near proximity to the compass needle of considerable masses of iron that were liable to have their position changed while the vessel was submerged."

To overcome the above-mentioned difficulties, Mr. Holland invented a device and was granted a patent (No. 492,960) for a triangular drag, which was expected to keep the vessel on a true course when under water. This triangular drag was the novel feature of Mr. Holland's 1893 design, and was intended automatically to steer the vessel on a straight course when submerged. It was intended to operate on the following ingenious principle:

While the vessel was running on the surface the steering gear was under the control of the steersman. In this condition the compass could be adjusted, as the vessel was on a substantially level keel and the masses of metal remained fixed in their relation to the compass, but when the vessel was caused to dive the masses of metal changed their relation to the adjusting magnets and the compass was thrown out of true. Therefore, on beginning a dive the vessel was first started on the surface on the course it was intended to follow submerged until the triangular drag, being drawn through the water, assumed a direction parallel to the axial line of the boat by reason of the rush of water against said drag, and especially against the rib thereon. As soon as the boat was on her course the steersman was expected to disconnect his hand steering gear and allow the drag to control the rudder to hold her to her original course. Mr. Holland maintained that any departure from a straight line would cause the drag to produce swinging motion of a lever, which was expected to throw the rudder in a reverse direction, thus returning the ship to her original course.

Another automatic steering device operated by the pressure of the water was expected to automatically control the depth of submergence, it being only necessary, theoretically, to move a control lever to a point on a dial corresponding to the desired or predetermined depth of submergence, and the horizontal diving rudder would then be automatically manipulated to incline the bow of the boat down so as to dive until the desired depth was reached and then to be manipulated to throw the bow up or down to maintain that depth.

In further describing his 1893 design for the Plunger, for which he received the award based on a guarantee of performance, Mr. Holland describes her as follows:

"The boat now being built for the United States Government satisfies all the requirements detailed earlier in this article. It will have a length over all of eighty-five feet, and diameter of eleven and one-half feet; total displacement, one hundred and sixty-eight tons, and a light displacement of one hundred and fifty-four tons. The guaranteed speed on the surface will be fifteen knots, the speed awash fourteen knots, and submerged eight knots. At full speed the boat will have an endurance of twelve hours and a radius of action of one thousand miles at slower speed. The endurance, when submerged, will be ten hours at a speed of six knots. The boat will be propelled by triple screws, operated by three independent sets of triple-expansion steam engines, capable of developing 1625 indicated horsepower. There will also be electric storage batteries and a motor of 70 horsepower for submerged running. The armament will consist of two expulsion tubes and five Whitehead torpedoes.

THE PLUNGER (HOLLAND TYPE SUBMARINE), LAUNCHED IN AUGUST, 1897

Machinery not drawn to scale. The engines of 1,600 horse-power, with the necessary auxiliaries, nearly filled the after portion of the vessel.