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first was merely a wooden box covered ports. This permits them to be shifted with two layers of glass with a small air so as to rest perpendicular to the sun at space between the layers. In the box the meridian. Such adjustments need was a miniature ether boiler. This gen- not be frequent, in fact not more than erator was exposed to the sun's rays, the once every two or three weeks. ether distilled and the amount of heat In an effort to concentrate every parwhich might be absorbed determined. ticle of sun ray possible, plane mirrors of Purely as an experiment a small engine cheap manufacture are so mounted on was run by this generator. The second two sides of the boxes that they reflect generator consisted of a two-inch steam upon the surface of the water vessel. pipe sixteen feet long, insulated at the This water vessel, itself is connected to a bottom and enclosed in a box covered by feed pipe at one end and a steam pipe at a double layer of glass. In this, also, the the other. The steam pipes from the ether was distilled and the number of various units of the plant are joined lisheat units absorbed was determined. The charging into an eight-inch main which third generator was made of a bed of carries the steam to the engine. water pipes, insulated against heat loss, The other factors of the sun-power the unit being eighteen by sixty feet, and plant are of ordinary construction. The the motor being an ether engine. This engine is a new type, low pressure, reapparatus yielded three and one-half ciprocating steam engine of great steam horse-power. From these experiments, economy. With it is a condenser and which are cited merely to show the foun- auxiliaries such as are in use in any condation of the present perfect machine, the densing plant. There is a continuous knowledge for the practical sun-power closed circuit, the water in the condenser plant was gained.
being pumped back into the absorber. The 10,000 power plant which goes to The first plant supplies the power for Egypt consists of an absorber, a low- an ordinary steam pump and whenever pressure engine, a condenser and auxili the sun shines this power has pumped aries. It is divided into a number of steadily and effectively. It has held up separate units.
steadily, under all tests, to the capacity of The absorber, roughly speaking, is 3,000 gallons a minute, lifted to a height divided into a series of units, each con of 33 feet. taining a flat, metal, honey-comb water Such is the sun-power plant, itself. Its vessel, rectangular in shape, looking commercial possibilities are limitless and much like a huge wafer with holes in it. even its manufacturing future is a matter A wooden box, with two layers of glass bounded by the imagination alone. having a one-inch air space between them Only during the overflow of the Nile for a covering, is the setting for the does Egypt have sufficient water to dewater vessel. Under the surface of this velop her wonderful agricultural rebox comes the insulation which prevents sources. Irrigation is done by laborers, heat loss. This is made of a two-inch thousands of them being used in the terlayer of regranulated cork and two layers ritory. The commissioner of the Khedive of water-proof cardboard.
believes that this one sun-power plant These boxes are elevated some thirty will take the place of over 2,500 laborers inches from the ground and rest on sup- and will give what Egypt has never yet
had—water at all times and in regulated work and has done it well. But in Philaand necessary quantities.
delphia, the plant has been tested under And the cost will be inconsequential adverse conditions. It is looked upon to compared to the cost of obtaining water do much more in a climate where the in arid countries. This is the great point temperature is 100 degrees Fahrenheit, as the real factor on which the sun-power it is in the tropics. plant may expect to build its success. From the absorber of 26 banks of Cost of water, the hardship of getting units, each containing 22 single units and water even at any cost, has been the key- having a light absorptive area of 10,296 note of the stories of disaster and trial square feet and an actual area of 5,148 which have so often filled the history of square feet, there has been developed at the development and abandonment of Tacony during eight hours running of certain sections of the Far West. Pri the plant, 4,825 pounds of steam. This vate companies and governments have was in a temperature of slightly more spent hundreds of thousands, aggregat than one-half of that in those hotter ing many millions in development plans, countries in which the sun-power plant is constructed great dams, turned the expected to do its best work. courses of rivers and ended, even then, “It will be of interest to know,” said oftentimes in failure.
Mr. Shuman, in discussing the cost of But the sun-power plant brings water his plant and its commercial possibilities, power right at hand even in the most "what the comparative cost of sun power arid districts. The terrors of Death and coal power is, in the tropics, as far Valley would yield to irrigation. But the as our present knowledge and present cost of irrigation has been too great. developments go. There was no way to force the water “The sun-power plant must, of course, into the sand wastes and bad lands. Here be a condensing plant, as steam above the sun-power plant will have its use. atmospheric pressure cannot practically
Texas, the state where irrigation has be used. I have assumed in estimating, made the fortunes of thousands, where that the 100 horse-power sun plants to crops may be grown the year round if be sent to Egypt and ordered for shipthere is water enough, will use the sun- ment elsewhere, are to be complete in power plant. For there are sections of every detail, covering also the pumps Texas where irrigation cost is too great necessary for using the power generated to permit the use of irrigation now. for irrigating purposes. In order to put
In Africa, in South America, in Mex- the coal plant on the same basis, I have ico, it is the same cry of water, water. assumed a simple form of modern comBut the cost has been too great. The pound condensing engine, with good sun-power plant is expected to solve this economy for such small powers, viz.: 3 difficulty also.
pounds of coal per brake horse-power. These are no dreams or the making of This coal plant is also to be fully equipdreams but proven facts, established by ped with all condensing apparatus and the orders that have come in for sun- pump for utilizing the power for irrigatpower plants. The orders have come be- ing purposes. They are both to be based cause the sun-power plant has done its on running eight hours per day, to be
manufactured in Philadelphia, in portable plant, would bring the cost of this coal shape, and erected at some fairly accessi- to $2.66 per ton; showing that wherever ble point in the tropics.
coal can be obtained at a cost of $2.66 "The comparison would then stand as per ton, both the sun plant and the coal follows:
plant would be equal competitors. Cost OF OPERATING 100 HORSE-POWER The great savings which would occur
Sun PLANT FOR ONE YEAR. through the use of the sun-power plants, Original cost of plant........$20,000.00 consist in the fact that through vast Interest on $20,000 at 5%.... 1,000.00 regions of the tropics coal varies from Wear and tear at 5% per an
$5.00 per ton at the most accessible num ........
seaports to as high as $30.00 at inaccesOne engineer, 350 days at
sible points. At the general average it $5.00 ................... 1,750.00 might as well be assumed that coal
throughout great areas of the tropics will Total .................$23,750.00 average $15.00 per ton; and here lies the Cost OF OPERATING 100 HORSE-POWER great field for sun power. COAL PLANT FOR ONE YEAR.
"Coal in the Chilean nitrate districts Original cost of plant........$10,000.00 for instance, I have been officially inInterest at 5%.............. 500.00
500.00 formed, costs $14.60 per ton, and there is Wear and tear at 5% per an
room for 100,000 horse-power in this num .................... 500.00 region alone.” One engineer,350 days at $5.00 1,750.00 An idea of the confidence which Mr.
Shuman has in the possibilities of his Total .................$12,750.00 sun-power plants is made clear in this "The above comparison shows it would statement : cost $1,000 per year more to operate a “The further development of solar sun plant than a coal plant, and do the power has no limit. Where great natural same amount of work. All minor ex- water powers exist, sun power cannot penses, such as lubrication, etc., are the compete; but sun-power generators will, same in both plants.
in the near future, displace all other "The 100 horse-power coal plant, based forms of mechanical power over at least on a coal consumption of 3 pounds per 10 per cent of the earth's land surface; brake horse-power hour, would burn and in the far distant future, natural during the year 375 long tons of coal. fuels having been exhausted, it will This, when divided into the $1,000 which remain as the only means of securing the sun-power plant costs above the coal heat for the human race."
HITTING BELOW THE BELT
ROBERT G. SKERRETT.
pretty nearly certain to mean Cleland Davis, U.
death. Popularly expressed, S. Navy, has in
in round terms this is the vented a revolu
essential difference between tionary torpedo,
the ordinary automobile torwhich profits by all that has
pedo and the weapon which been done in the art of war
Commander Davis has brought toward increasing the speed
into being. and the range and the pre
The new torpedo carries cision of attack of this instru
within its head a gun capable ment of destruction. It does
of discharging a projectile of away with the explosive charge
eight-inch caliber, which can of guncotton which has so
be loaded with a high explolong been the torpedo's means
sive, and which can be imof working havoc when once it had pelled with sufficient velocity to carry it reached its mark. In place of the gun- through several inches of steel. It cotton warhead, Commander Davis sub- actually amounts to reducing the battle stitutes a gun capable of firing an explo range of the usual service eight-inch sive shell—the projectile being designed rifle and in placing the gun, therefore, to burst after it has pierced the hull right against the least protected approach plating of the enemy's vessel, and, found to the seat of life of an enemy's ship. its way to the ship's vitals, such as her Now it takes ordinarily a gun of pretty engines, boilers, magazines or shell heavy weight and thickness of walls to rooms. Cunning construction of battle- provide the muzzle energy with which to ships has substantially neutralized the carry out Commander Davis' idea-in powers of the ordinary torpedo, notwith- fact, a larger and more ponderous standing the fact that the deadly load in weapon than could be borne within the the warhead has been largely increased; limits of the usual service torpedo, big but the Davis gun torpedo has again as they have grown to be. However, here brought about a crisis, and the mightiest is where the metallurgist unconsciously of modern dreadnaughts have now a new paved the way for the new torpedo. The menace to face. The blow of a fist over gun in the Davis weapon is made of the heart or upon the head may render vanadium steel, and this composition furthe victim unconscious, but a dagger nishes all of the needful strength in comthrust or a bullet in either one of these is bination with remarkable lightness: in
DIAGRAM OF THE REGULAR WHITEHEAD TORPEDO, SHOWING THE GUN-COTTON
CHARGE IN ITS HEAD. The new torpedo, the Davis, does not use this gun-cotton bead. The Whitehead torpedo is not necessarily fatal to the
vessel against whose side it explodes.
sufficient remairing velocity to carry it through the oi 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 objectivepossibly 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
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
CROSS SECTION OF A RUSSIAN BATTLESHIP INJURED
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 bulk head. and
Dot ruptured by the same force
of the explosive gases.