This is the basic principle of the Radio Compass. In using it, the loop is swung, first, in one direction until the sound received from the detector is loudest; then in the other direction until the sound received there reaches a maximum; and, finally, the angle between these two maxima is bisected, and the plane of the loop if set at this mid position will be pointing directly at the station from which the wireless wave emanated.

This compass has been so perfected that it is possible to steer a ship into port in any weather by its use. Recently, one of our naval vessels got its position in foggy weather from the station at Cape May, 280 miles distant.

Radio for Aircraft.-Radio telegraphic apparatus for seaplanes has been developed which is efficient for ranges up to 200 miles, and for dirigibles up to 600 miles. Radio telephone sets, having ranges one-half those of the telegraphic sets, have also been developed. A trailing wire is used as an antenna.

Communication between planes in flight is possible up to ranges of 75 miles by wireless telegraph and 50 miles by telephone. The most satisfactory radio telephone for seaplanes is the product of the General Electric Company. Radio telephones have been installed on virtually all our naval vessels, the type used being principally that furnished by the Western Electric Company. The radio telephone has been especially valuable for manoeuvering hunting squadrons of submarine chasers and seaplanes.

A radio compass has also been developed by the Bureau engineers for the purpose of determining direction by radio signals received in an airplane. The instrument gives fairly accurate direction up to 500 miles when the plane is in flight and is exceedingly valuable for aircraft navigation.

REPAIR OF THE GERMAN MERCHANT SHIPS DAMAGED BY THE VANDALISM OF THEIR CREWS.

The almost incredibly rapid repair of the German merchant vessels lying in our ports and seized by our Government when

we entered the war makes one of the most striking and dramatic stories in the history of naval engineering. I am unable to give it in full, since the Secretary of the Navy will treat the matter at some length in his forthcoming Annual Report, and I may not anticipate his statement. I will, however, give some details-engineering mainly-which will probably not be embodied in that report.

The views which will be shown comprise: one showing the use of oxyacetylene welding in the repair of some of the large main cylinders of these ships, and others illustrating the repair by electric welding of broken parts of the machinery of the ex-German steamer Santos.

The Santos, I should state, is not one of the vessels seized by our Government. When war broke out, 46 German merchant ships were interned in Brazilian harbors. When Brazil entered the war its government seized these ships, but not before some damage had been done to their machinery by their crews. Later, Brazil turned over 29 of these vessels to the French Government. One of them, the Santos, could not be repaired with the facilities available at Rio Janeiro, since her machinery was virtually a heap of junk.

So the French naval attaché at Washington appealed to our Navy Department, and, at the suggestion of the Engineer-inChief, the broken parts of the Santos machinery were crated and shipped to the Philadelphia Navy Yard, where they were repaired by electric welding under the supervision of Captain Clarence A. Carr, Engineer Officer of that yard, through whose courtesy I am enabled to show the Santos views tonight. Their value lies in the fact that they form a complete series, illustrating fully the methods used by our Navy in repairing the ships we seized, except that, in most cases, our work was done on the broken cylinders while they were in place and the engines were not dismantled.

There were, in all, 103 of these German ships seized by our Government. Of this number about 50 were turned over to

the Navy by the Shipping Board for repairs. The major damage inflicted was the breaking of cast-iron parts of the main engines, chiefly the cylinders. But, in addition, some connecting rods, piston rods, and boiler stays were sawed through, boilers were burned out by dry firing, and there was much minor vandalism.

The chief problem, however, was the repair of the broken cylinders, some of which were more than nine feet in diameter. The Bureau estimated that with such facilities as were available for this heavy work it would take at least eighteen months to replace the damaged cylinders by new ones. Meanwhile there was bitter need of rapid transport for our troops to France. On the removal of that crisis there seemed to depend the salvation of Christendom.

At this juncture, Captain Earl P. Jessop, then Engineer Officer of the New York Navy Yard, recommended that repairs be made by welding, and in this recommendation he was heartily supported by Rear Admiral George E. Burd, Industrial Manager of that yard. The Engineer-in-Chief at once ordered Captain Oscar W. Koester, Assistant to the Bureau, to New York to investigate the situation fully. As the result of his report the Bureau immediately issued orders to make repairs, where possible, by electric or oxyacetylene welding, and where welding was impracticable owing to the location of the break, to resort to mechanical patching-that is, to "soft patches" secured by body-bound bolts.

From this stage onward the Engineer-in-Chief placed the repairs under the personal supervision of Captain Koester, who in his resourceful ability and driving power is unsurpassed. His work went on night and day, and in five months he traveled about 14,000 miles in railroad trains from one navy yard or private plant to another along our Atlantic coast. At the expiration of that period, his huge work was done and the ships were ready for service.

As soon as repairs were completed on each vessel the

strength of the new seams was tested under the full pressure of the original design, and none failed. She was then sent to sea on a minimum trial run of 48 hours under full power, the instructions to her officers being to break down the machinery by legitimate over-work, if they could. Every engine on every vessel withstood all tests, and the ships have been in continuous service since then.

Some few of these large cylinders-about ten, I believe— were repaired by oxyacetylene welding. This method was abandoned, however, not because of the quality of the weld, but because the method did not suit the conditions. With it the cylinder had to be dismantled and removed, and then, owing to the size of the flame, the huge mass of metal had to be pre-heated. These conditions did not exist with the electric arc, whose welding point is very small and can be localized, and whose temperature can be absolutely controlled.

As to the employment of the electric arc for this purpose, this method is too well known for description here. Its use, however, on such an extensive scale was unprecedented, and great credit is due the staff of the welding company who did so rapidly such perfect and, at the time, such vital work, and also to the officials of that company, who personally coöperated with the Navy in this great undertaking.

The rapidity of getting these ships ready for service was facilitated by one other action. On many of them, in addition to the damage done by vandalism, extensive repairs were necessary, owing to their deterioration from long idleness. As the necessary overhaul and all routine repairs could be made by a capable naval crew under able officers, the Engineer-inChief laid the matter before Admiral Benson, Chief of Operations, with the request that the ships be fully commissioned before repairs were begun. This was done, and thus while the welding operations were in progress the ships were prepared in all other respects for sea.

One other feature of this matter deserves comment, and

that is the military value of this work in the transport of troops. These fifty ships were in service for about a year before hostilities ended, and this is approximately the time saved in these repairs by using welding methods. Twenty of these vessels can carry about 70,000 troops in one trip, and ten round trips a year is a conservative estimate of their performance. Representative Young, of North Dakota, who crossed the Atlantic in the Leviathan, stated recently in the House that she had transported more than 99,000 troops up to August 20. So it may be justly claimed that the rapidity of these repairs had a marked effect on the early end of the fighting in France.

It is true that criticism was leveled at the Bureau for using these welding methods, and, too, by not a few engineers and shipbuilders. But the answer to all criticisms from every source is that the ships are running, without accident or delay.

THE ELECTRIC DRIVE FOR BATTLESHIPS.

In those stormy days toward the end of the Civil War, Isherwood, that master engineer, designed for the United States Navy the 17-knot cruisers Wampanoag and her sisters, which, as their trials proved, were incomparably the fastest ships, naval or merchant, at that time in the world. The jealousy and ignorance of those days of semi-sail power brought down on him a storm of criticism, and ultimately the great Engineer-in-Chief was forced to see his peerless ships rot at their moorings.

In the years since then there has been no fit comparison with this shameful episode in our naval history, except, in less degree, the similar storm which burst on the head of the present Engineer-in-Chief, when, with high courage and far vision, he urged the introduction of the electric drive for the propelling machinery of battleships and battle cruisers.

In one vital element, however, there was a radical difference between these two historic controversies. Isherwood was