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first was merely a wooden box covered with two layers of glass with a small air space between the layers. In the box was a miniature ether boiler. This generator was exposed to the sun's rays, the ether distilled and the amount of heat which might be absorbed determined. Purely as an experiment a small engine was run by this generator. The second generator consisted of a two-inch steam pipe sixteen feet long, insulated at the bottom and enclosed in a box covered by a double layer of glass. In this, also, the ether was distilled and the number of heat units absorbed was determined. The third generator was made of a bed of water pipes, insulated against heat loss, the unit being eighteen by sixty feet, and the motor being an ether engine. This apparatus yielded three and one-half horse-power. From these experiments, which are cited merely to show the foundation of the present perfect machine, the knowledge for the practical sun-power plant was gained.

The 10,000 power plant which goes to Egypt consists of an absorber, a lowpressure engine, a condenser and auxiliaries. It is divided into a number of separate units.

The absorber, roughly speaking, is divided into a series of units, each containing a flat, metal, honey-comb water vessel, rectangular in shape, looking much like a huge wafer with holes in it. A wooden box, with two layers of glass having a one-inch air space between them for a covering, is the setting for the water vessel. Under the surface of this box comes the insulation which prevents heat loss. This is made of a two-inch layer of regranulated cork and two layers of water-proof cardboard.

These boxes are elevated some thirty inches from the ground and rest on sup

ports. This permits them to be shifted so as to rest perpendicular to the sun at the meridian. Such adjustments need not be frequent, in fact not more than once every two or three weeks.

In an effort to concentrate every particle of sun ray possible, plane mirrors of cheap manufacture are so mounted on two sides of the boxes that they reflect upon the surface of the water vessel. This water vessel, itself is connected to a feed pipe at one end and a steam pipe at the other. The steam pipes from the various units of the plant are joined discharging into an eight-inch main which carries the steam to the engine.

The other factors of the sun-power plant are of ordinary construction. The engine is a new type, low pressure, reciprocating steam engine of great steam economy. With it is a condenser and auxiliaries such as are in use in any condensing plant. There is a continuous closed circuit, the water in the condenser being pumped back into the absorber.

The first plant supplies the power for an ordinary steam pump and whenever the sun shines this power has pumped steadily and effectively. It has held up steadily, under all tests, to the capacity of 3,000 gallons a minute, lifted to a height of 33 feet.

Such is the sun-power plant, itself. Its commercial possibilities are limitless and even its manufacturing future is a matter bounded by the imagination alone.

Only during the overflow of the Nile does Egypt have sufficient water to develop her wonderful agricultural resources. Irrigation is done by laborers, thousands of them being used in the territory. The commissioner of the Khedive believes that this one sun-power plant will take the place of over 2,500 laborers and will give what Egypt has never yet had—water at all times and in regulated and necessary quantities.

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FRONT VIEW OF THE ENGINE. AUXILIARIES AND WATER PUMP THAT FIND A MOTIVE

POWER FROM THE SUN'S HEAT.

And the cost will be inconsequential compared to the cost of obtaining water in arid countries. This is the great point, the real factor on which the sun-power plant may expect to build its success. Cost of water, the hardship of getting water even at any cost, has been the keynote of the stories of disaster and trial which have so often filled the history of the development and abandonment of certain sections of the Far West. Private companies and governments have spent hundreds of thousands, aggregating many millions in development plans, constructed great dams, turned the courses of rivers and ended, even then, oftentimes in failure.

But the sun-power plant brings water power right at hand even in the most arid districts. The terrors of Death Valley would yield to irrigation. But the cost of irrigation has been too great. There was no way to force the water into the sand wastes and bad lands. Here the sun-power plant will have its use.

Texas, the state where irrigation has made the fortunes of thousands, where crops may be grown the year round if there is water enough, will use the sunpower plant. For there are sections of Texas where irrigation cost is too great to permit the use of irrigation now.

In Africa, in South America, in Mexico, it is the same cry of water, water. But the cost has been too great. The sun-power plant is expected to solve this difficulty also.

These are no dreams or the making of dreams but proven facts, established by the orders that have come in for sunpower plants. The orders have come because the sun-power plant has done its

work and has done it well. But in Philadelphia, the plant has been tested under adverse conditions. It is looked upon to do much more in a climate where the temperature is 100 degrees Fahrenheit, as it is in the tropics.

From the absorber of 26 banks of units, each containing 22 single units and having a light absorptive area of 10,296 square feet and an actual area of 5,148 square feet, there has been developed at Tacony during eight hours running of the plant, 4,825 pounds of steam. This was in a temperature of slightly more than one-half of that in those hotter countries in which the sun-power plant is expected to do its best work.

"It will be of interest to know," said Mr. Shuman, in discussing the cost of his plant and its commercial possibilities, "what the comparative cost of sun power and coal power is, in the tropics, as far as our present knowledge and present developments go.

"The sun-power plant must, of course, be a condensing plant, as steam above atmospheric pressure cannot practically be used. I have assumed in estimating, that the 100 horse-power sun plants to be sent to Egypt and ordered for shipment elsewhere, are to be complete in every detail, covering also the pumps necessary for using the power generated for irrigating purposes. In order to put the coal plant on the same basis, I have assumed a simple form of modern compound condensing engine, with good economy for such small powers, viz.: 3 pounds of coal per brake horse-power. This coal plant is also to be fully equipped with all condensing apparatus and pump for utilizing the power for irrigating purposes. They are both to be based on running eight hours per day, to be

SJ manufactured in Philadelphia, in portable shape, and erected at some fairly accessible point in the tropics.

"The comparison would then stand as follows:

Cost Of Operating 100 Horse-power Sun Plant For One Year.

Original cost of plant $20,000.00

Interest on $20,000 at 5%.... 1,000.00 Wear and tear at 5% per annum 1,000.00

One engineer, 350 days at $5.00 1,750.00

Total $23,750.00

Cost Of Operating 100 Horse-power Coal Plant For One Year.

Original cost of plant $10,000.00

Interest at 5% 500.00

Wear and tear at 5% per annum 500.00

One engineer,350 days at $5.00 1,750.00

Total $12,750.00

"The above comparison shows it would cost $1,000 per year more to operate a sun plant than a coal plant, and do the same amount of work. All minor expenses, such as lubrication, etc., are the same in both plants.

"The 100 horse-power coal plant, based on a coal consumption of 3 pounds per brake horse-power hour, would burn during the year 375 long tons of coal. This, when divided into the $1,000 which the sun-power plant costs above the coal

plant, would bring the cost of this coal to $2.66 per ton; showing that wherever coal can be obtained at a cost of $2.66 per ton, both the sun plant and the coal plant would be equal competitors.

The great savings which would occur through the use of the sun-power plants, consist in the fact that through vast regions of the tropics coal varies from $5.00 per ton at the most accessible seaports to as high as $30.00 at inaccessible points. At the general average it might as well be assumed that coal throughout great areas of the tropics will average $15.00 per ton; and here lies the great field for sun power.

"Coal in the Chilean nitrate districts for instance, I have been officially informed, costs $14.60 per ton, and there is room for 100,000 horse-power in this region alone."

An idea of the confidence which Mr. Shuman has in the possibilities of his sun-power plants is made clear in this statement:

"The further development of solar power has no limit. Where great natural water powers exist, sun power cannot compete; but sun-power generators will, in the near future, displace all other forms of mechanical power over at least 10 per cent of the earth's land surface; and in the far distant future, natural fuels having been exhausted, it will remain as the only means of securing heat for the human race."

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HITTING BELOW THE BELT

By

ROBERT G. SKERRETT

COMMANDER Cleland Davis, U. S. Navy, has invented a revolutionary torpedo, which profits by all that has been done in the art of war toward increasing the speed and the range and the precision of attack of this instrument of destruction. It does away with the explosive charge of guncotton which has so long been the torpedo's means of working havoc when once it had reached its mark. In place of the guncotton warhead, Commander Davis substitutes a gun capable of firing an explosive shell—the projectile being designed to burst after it has pierced the hull plating of the enemy's vessel, and, found its way to the ship's vitals, such as her engines, boilers, magazines or shell rooms. Cunning construction of battleships has substantially neutralized the powers of the ordinary torpedo, notwithstanding the fact that the deadly load in the warhead has been largely increased; but the Davis gun torpedo has again brought about a crisis, and the mightiest of modern dreadnaughts have now a new menace to face. The blow of a fist over the heart or upon the head may render the victim unconscious, but a dagger thrust or a bullet in either one of these is

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Photograph Taken Just As A Shell Hit Its Target.

pretty nearly certain to mean death. Popularly expressed, in round terms this is the essential difference ■ between the ordinary automobile torpedo and the weapon which Commander Davis has brought into being.

The new torpedo carries within its head a gun capable of discharging a projectile of eight-inch caliber, which can be loaded with a high explosive, and which can be impelled with sufficient velocity to carry it through several inches of steel. It actually amounts to reducing the battle range of the usual service eight-inch rifle and in placing fhe gun, therefore, right against the least protected approach to the seat of life of an enemy's ship. Now it takes ordinarily a gun of pretty heavy weight and thickness of walls to provide the muzzle energy with which to carry out Commander Davis' idea—in fact, a larger and more ponderous weapon than could be borne within the limits of the usual service torpedo, big as they have grown to be. However, here is where the metallurgist unconsciously paved the way for the new torpedo. The gun in the Davis weapon is made of vanadium steel, and this composition furnishes all of the needful strength in combination with remarkable lightness: in

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DIAGRAM OF THE REGULAR WHITEHEAD TORPEDO. SHOWING THE GUN-COTTON

CHARGE IN ITS HEAD.

The Dew torpedo, the Davis, does not use this gun-cotton head. The Whitehead torpedo is not necessarily fatal to the

vessel against whose side it explodes.

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brief, makes the gun-torpedo practicable. In an ordinary gun, vanadium steel would not do because it would soon be damaged by the intense heat of the powder gases—that being one of the penalties of using this alloy; but a torpedo in time of war is expected to operate only once, so the life limit of this new steel does not concern Commander Davis, provided the gun can do its work well when it makes its single attack.

In foreign navies, it is the wellnigh universal practice to further safeguard their ships from torpedoes by lowering defense nets. These nets are held off from the sides of the ships by means of booms, their meshes are fashioned of tough metallic links, and they are generally sufficient to halt the torpedo in its flight and to cause it to explode at arm's length, so to speak, where it can do but little if any damage. Now the same netting would also cause the Davis torpedo to function, i. e., the gun would be fired and the explosive shell expelled, but the subsequent effects would be quite different from those of its usual rivals. The projectile would easily pass through the torpedo netting, traverse the intervening water, and strike the bottom plating with

sufficient remair.ng velocity to carry it through the 01 posing steel and into the craft's vital interior, where it could burst into many pieces and spread havoc. In order that the shell may do this, it carries what is known as a delayed-action fuse, which withholds the ignition of the bursting charge until a definite interval of time has passed. To a layman a fiftieth or a hundredth of a second is meaningless, but to the ordnance engineer it is an appreciable period.

It was only a few years ago when the maximum effective range of the torpedo was something like 1,800 yards—the attacking craft had to get that close to her objective—possibly in the face of searchlights and the withering blast from a battery of quick-firing guns. Today, thanks to improvements in the motive power and the superheating of the compressed air impulse, torpedoes have accredited ranges all the way from 4,000 to 7,000 yards—rumor being responsible for a possible range of even 10,000 yards in the latest of European torpedoes. Now

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Cross Section Of A Russian Battleship Injured

In The War With Japan By The Explosion

Of A Submarine Mine. But Not

Fatally Damaged.

D. A. shows the damaged area where the outer and the

inner bottom platings were shattered. A. marks

the position of a protective bulkhead, and

A1, the same bulkhead bent inward but

not ruptured by the same force

of the explosive gases.

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