Germany's most successful and highly developed class of submarine has been, of course, the U-boat type of submersible. These are the terrors of the sea which have succeeded in crossing the Atlantic, and have been developed both as the fighting and as the commercial U-boat. Herr Schmidt reported that Germany was constructing submarines 25 per cent larger than anything the United States had ever seen or heard of. His information was to the effect that Germany had a building capacity for ten submarines a week. The ability to produce these boats with such rapidity is due to the process of standardization--the practice of modern efficiency which has made it possible for American factories to turn out such big quantities of automobiles in a limited period. All parts of the German U-boats are made in standard sizes and from the same original pattern. Consequently, these parts are turned out by machinery in replica, and the building of the finished boats is merely a matter of assembling them at points to which the various parts have been shipped. The Diesel oil engine, which is regarded as the ideal power-producing engine for submarines, has been developed to its highest state of efficiency by Germany, and is made at the famous Krupp gun works, the great engine works in Augsburg, Emden and Nuremburg, and other less well-known places in Germany. It has been estimated that Germany has anywhere from 250 to 500 submarines, and it is said that the aim is to produce 1000 of these craft, to absolutely destroy the commerce of the seas and starve into submission England and France. HOW SUBMARINES WORK. According to Herr Schmidt, the submarines work in groups of four. Because of the limited capacity of the boats for carrying provisions, supplies and fuel, it is necessary for them to have supply bases, to which they can return and secure torpedoes. In operation each group consists of four submarines, traveling along in a diamond-shaped formation, one in front, one on either flank and one in rear. Eight miles separate the boats. The leading submarine carries the extra gasoline and supplies and acts as a scoutship; she sights a vessel, reports its speed and direction and then submerges--her task is done. The two torpedo carriers on either flank immediately change their courses so as to converge on the prey, and they arrive one on either side of her--they get her in between them. The boat in the rear keeps them informed as to the doomed ship's progress, and submerges at the last moment. She carries the extra crews for the fighting pair. The U-boats are fairly well protected against the onslaught of the light torpedo-boat destroyers and chasers, because the decks are protected by several feet of water at almost all times, while the commanding tower is covered with from two to three inches of the best steel armor plate.