Propelled on the surface by a fifty horse-power gasoline motor, the _Holland_ had a cruising radius of 1500 miles at a speed of seven knots an hour. Submerged, she was driven by electric storage-batteries. This effective combination of oil-engines with an electric motor is one of John P. Holland’s great discoveries, and is used in every submarine to-day. When her tanks were filled till her deck was flush with the water, and the two horizontal rudders at the stern began to steer her downwards, the _Holland_ could dive to a depth of twenty-eight feet in five seconds. She had no periscope, for that instrument was then crude and unsatisfactory. To take aim, the captain of the _Holland_ had to make a quick “porpoise dive,” up to the surface and down again, exposing the conning-tower for the few seconds needed to take aim and judge the distance to the target. Though by this means the _Holland_ succeeded in getting within striking-distance of the _Kearsarge_ and the _New York_ without being detected, during the summer manœuvers of the Atlantic fleet off Newport in 1900, it has proved fatal to the only submarine that has tried it in actual warfare (see page 160). Less than half the length of the _Nordenfeldt II_, the _Holland_ did not pitch or see-saw when submerged. Each of her crew of six sat on a low stool beside the machinery he was to operate, and there was no moving about when below the surface. Neither did the boat stand on her tail when a torpedo was discharged from the bow-tube, for the loss of weight was immediately compensated by admitting an equivalent amount of water into a tank. Originally the _Holland_ had a stern torpedo-tube as well, besides a pneumatic gun for throwing eighty pounds of dynamite half a mile through the air, but these were later removed. How the _Holland_ impressed our naval officers at that time is best shown in the oft-quoted testimony of Admiral Dewey before the naval committee of the House of Representatives in 1900. “Gentlemen, I saw the operation of the boat down off Mount Vernon the other day. Several members of this committee were there. I think we were all very much impressed with its performance. My aid, Lieutenant Caldwell, was on board. The boat did everything that the owners proposed to do. I said then, and I have said it since, that if they had had two of those things at Manila, I could never have held it with the squadron I had. The moral effect--to my mind, it is infinitely superior to mines or torpedoes or anything of the kind. With those craft moving under water it would wear people out. With two of those in Galveston all the navies of the world could not blockade the place.” [Illustration: Photo by Brown Bros. John P. Holland.]