figures of killed and wounded in this raid are given as sixty-seven killed, and 117 injured.

During the month of July, reports of the new German superZeppelins began to appear in British reports, and a number of neutral correspondents endeavored to obtain authentic data concerning them. Conflicting descriptions arrived from many sources, and it was not until a Swiss reporter, equipped with extremely powerful glasses, watched the trial flights of two of these super-Zeppelins above Lake Constance, that fairly reliable information could be compiled.

One of these airships leaves Friedrichshafen every week for duty in the North Sea, and the factory on the shore of Lake Constance expects to be able to complete five machines every month after July, 1916. The super-Zeppelin has two armored gondolas, without a visible connection, although it is highly probable that such communication is provided for within the outer envelope. Each gondola carries six machine guns and, in addition, two quick-firing guns, as well as an aerial torpedo-launching device, which was first used in the extensive air raids on England in the last week of July.

The super-Zeppelin contains approximately 1,000,000 cubic feet of gas and has a capacity of ten tons useful load. Of this load, about four tons can be composed of bombs or other munitions, the remainder being needed for fuel, machinery, and the crew, as well as ballast and provisions. The gross weight of a fully equipped and loaded super-Zeppelin is thirty tons, or roughly, 60,000 pounds. The envelope, which heretofore has been painted gray with liquid aluminum paint, now is impregnated thoroughly with finely divided metal, by means of the Schoop metal-coating process, which is heralded as one of the most farreaching improvements in aerial navigation. By its means the airship envelope is made absolutely impervious to atmospheric influences.

For its protection against antiaircraft fire the new super-Zeppelins carry apparatus in each gondola, producing artificial clouds of such size and intensity as to envelop and shroud completely the entire airship, rendering it absolutely invisible from below.

While this cloud expands and gradually grows thinner, the airship rises rapidly in a vertical direction, speeding away while under protection of the self-made clouds.

The motors of the latest Zeppelins weigh only 595 pounds each, although developing 240 horsepower, which means that one horsepower is developed for every three and three-quarter pounds of metal used. They are fitted with twin pumps, double jet carburetors, and are usually operated on mixtures consisting of one part benzol with one part alcohol.

THE

AEROPLANE

CHAPTER LIV

IMPROVEMENTS GIANT

MACHINES-TECHNICAL

DEVELOPMENTS

HE experience gathered in the first eighteen months of the war by the aviators of the hostile armies has done more for the development of aeroplanes than many years of peaceful improvements could possibly have accomplished. The ever increasing size, power and stability of the heavier-than-air machine is plainly shown in the latest types of battle planes, in which a spread of wings exceeding seventy-five feet is no longer a novelty. True, the heralded approach of the gigantic German battle triplanes did not take place in the second year of the Great War, although it is an incontrovertible fact that such machines have been built and are being used for some purpose. But none of them took part in the fighting on the western front, nor has one of them been seen on the Russian battle lines. There is reason to believe, however, that these planes are used in naval reconnoitering, and their great size permits of the carrying of large supplies of fuel, giving them a great cruising radius. Reports from steamers plying the Baltic state that gigantic aeroplanes have been sighted high up in the air by captains and officers on Swedish and Danish ships, seemingly maintaining a careful

patrol of that sea against possible Russian and British naval exploits.

There have been numerous unconfirmed reports concerning the use of cellon, a tough and yet completely transparent material, in the construction of aeroplanes on the German side, and occasional hints of new "invisible" machines were dropped now and then. The reports probably are based on some foundation of fact, but there is little to show that cellon is used to any large extent by the Teuton forces. Samples of the material reached New York late in 1915, but the actual uses to which it was put were not known at the time.

The tendency in recent months, especially on the western battle front, has been the "attack in squadrons,” instead of the individual combats which made international heroes out of Boillot, Immelmann, Boelke, Warneford and Navarre. The squadron attack was first employed by the Germans in the Verdun operations. Previous to that time, only bombing expeditions had been undertaken en masse, as many as sixty aeroplanes taking part in a single attack. But actual aerial combat usually engaged only two or four aviators.

Early in February of the second year of the war, several famous French aviators fell victims to the new mode of warfare. It seems that as soon as a machine would appear above the trenches in that section, six or more German machines would rise quickly and surround the Frenchman. Outnumbered and surrounded on all sides the French machines rarely got back safely to their lines, among the first to be lost being George Boillot, world-famous as an automobile racer.

The German tactics at once were imitated and improved on by the allied forces, and by July, 1916, the French had perfected a system of defense which, paradoxically speaking, may be termed "air-tight." French aviation squadrons would be held in readiness at all times to repel attacks, and twenty machines usually were considered a “unit." At first sign of a hostile aeroplane approaching, ten French machines would rise at top speed to a height of 10,000 feet, while five minutes later the second ten would follow, rising to 5,000 feet. The attacking machine

usually would be found at a height intermediate between the upper and lower French squadrons, both of which would attack the invader vigorously, and with highly satisfactory results.

One of the lessons of these true aerial battles between opposing squadrons has been the efficiency of the biplane, as compared with that of the monoplane. When the war started the monoplane was considered the machine par excellence for war use; its high speed and quick maneuvering being cited as most important for fighting in the air. Eighteen months of aerial battles have shown that for all-round fighting, bombing and reconnoitering the biplane is far more effective, and the construction of new monoplanes has been practically abandoned by the allied governments. The Germans, it is true, have found the Fokker type of monoplane a very efficient one, but the number of Fokkers in use is comparatively small, when the great fleets of Aviatiks and other well-known types of German biplanes are remembered.

Exact statistics regarding the number of aeroplanes at present in use along the various battle fronts are not available, but estimates made by aviation officers, by correspondents and from notes in the respective publications, devoted to aviation abroad, fix it as in excess of 12,000 machines. More than half of these are used by the Allies on the western front; Germany is credited with 3,000 aeroplanes, Russia with about 1,000, Austria with 1,500, and Bulgaria and Turkey with 500. In a statement made in the British House of Commons, Mr. Tennant, speaking of the Royal British Flying Corps, declared that 835 officers and 521 civilians were on the waiting list of the Flying Corps in the last week of February, 1916.

France has definitely discontinued the use of monoplanes and is manufacturing them solely for the British forces, as some of the British aviators greatly prefer the monoplane. One of the reasons given by the French for their action is the construction of Fokker monoplanes by the Germans, which are so accurate a copy of the earlier Morane monoplanes of the French that they could not be distinguished from them in the air. Furthermore, the German copy of the Morane was far speedier and could easily outdistance or overtake the French machines of the same

type. In place of the original Morane France now has three types of speed planes, the Maurice Farman, a 110 mph. biplane, the Morane-Saulnier, 111mph., and Spad, 107 mph. The older Nieuports, too, are fast machines, being capable of more than 100 miles per hour.

The new Maurice Farman speed plane is a biplane of small wing area, the upper plane overhanging the lower. It is equipped with a new type of Renault-Mercedes eight-cylinder motor, giving 240 horsepower at the highest crank shaft speed. The Morane-Saulnier and the Spad are both monoplanes, but of different shape and construction from the original Morane; it is of the so-called monocoque type, made familiar to Americans by the Duperdessin monocoques which took part in the Gordon Bennett Cup race in Chicago in 1912. It is equipped with a device which was first used in Germany and which permits the firing of the gun through the propeller. It is an electric synchronizing device which fires the gun at the exact moment when the bullet will pass between the propeller blades.

Following the destructive raids of the German naval Zeppelins over the eastern counties of England during the last days of January, 1916, there came a period of retaliation flights by Allied aviators over German cities, attacks on railway stations and munition depots, culminating in the great attack of the coast of Schleswig-Holstein by a fleet of British aeroplanes. On a certain section of this coast the Germans have erected a series of Zeppelin hangars behind one of the most elaborate systems of defenses known at present. According to information which had reached the British admiralty, the German coast north of the Kiel Canal is protected at intervals by the most powerful antiaircraft artillery, including 4.1-inch guns, capable of firing thirty-five pound shells to a height of 26,000 feet at the rate of ten every minute. The risk which the British sea planes underwent was great, but there seems to have been no hesitation on the part of the aviators to fly to the attack.

Early in the morning of March 25, 1916, two sea-plane "mother ships," accompanied by a squadron of eight protected cruisers and fast destroyers under the command of Commodore Tyrwhitt,