SINCEthe successful launching on September 7th, 1911, of the hydro-aeroplane of the United States Navy, by sliding It down a wire, Mr. Curtiss has given his attention to new experiments in aviation of no less interest. On October 2nd he made a test of the stresses in the stay wires of all the panels of the main sustaining surfaces of his standard biplane, in order to compare them with the stresses, determined by computation and by graphical construction. To this end he turned the aeroplane upside down, supported it at its middle, and loaded the entire main planes with sand distributed in such manner as to produce in the guy wires the same stress as in ordinary flight. When subject to their full stress each wire was tested by means of a pair of tension tongs. These look like ordinary-blacksmith tongs except that each jaw is slitted so as to pass over the wire to be tested and grip it When the slits are closed by tightening screws. When the jaws were thus attached to a wire, the handles of the tension tongs were drawn together just enough to cause the bit of wire between the jaws to lose its stress, and slacken. The force on the long handles was then measured by a spring balance, which in fact caused them to exert the required stress, and the tension in the wire was found directly as the product of the force indicated by the spring balance multiplied by the ratio of the distances from the tongs pivot respectively to the spring balance and to the wire under test It had been previously shown by analysis and by graphic statistics, that in a biplane whose surfaces have practically a uniform running load from center to either wing tip, as may be roughly assumed to be true in ordinary usage, the stress in the outwardly and upwardly sloping stay wires of the end panels, or wing tips, 'sustain but one-fourth as much tension as the corresponding wires in the second panels from the end, while those wires which slope outwardly and downwardly sustain no material tension due to pressure on the concave side of the wings, though they may be very severely strained when the machine is jolting over rough ground. In the third section from either wing tip, known as the engine section, the tension in the guy wires and oblique stay rods is still greater, being more than five times the tension in the wires of the end panels. Though the test was made for practical rather than scientific purposes, the stresses were found to increase from .the wing ends to the engine section approximately as indicated by theory. It was observed also that each wire had a large factor of safety, ranging from about ten to thirty. Mr. Curtiss then added his weight of 150 pounds to one wing tip, while an assistant of equal weight stood on the other wing end. The stress in the wires of the second panel was then doubled. Other tests were made on the ribs of the main planes. It was noticed that they were sprung by the load of sand sufficiently to change the tension perceptibly in the fore-and-aft diagonal wires. Mr. Curtiss had a panel of the main planes placed upside down with its spars resting on trestles placed transversely to the ribs. When uniformly loaded with sand weighing ten times the usual pressure on the wings, these collapsed, due to breakage of the ribs. From these various tests it was concluded that the weakest part can endure ten times the stress it usually has to sustain ill ordinary flight. During the month of October Mr. Curtiss developed a new type of hydro-aeroplane, intended for pleasure and sociability. This has been called a “family hydro.” The machine consists of a biplane mounted directly on a single boat of unusual size, without intermediate framing, so that the lower plane rests directly on top of the boat amidships. The passengers will sit on the bow of the boat just before the lower plane. The engine will be mounted just underneath the upper plane so as to allow the propeller on its crankshaft to A plane loaded with gravel. swing freely without too near exposure to the back of the boat and the spray thrown up when the latter is skimming the water rapidly. The usual floats at the wing ends will be used to preserve the lateral balance when the vessel rests quietly on the water, or runs over its surface. The final goal is an aeroplane which can be manipulated as readily as a motor boat, which can be launched from smooth or rough water alike, and which, after a substantial voyage in the air, may be landed on earth or water with ease and security. A novel wind-tube for studies in aerodynamics was developed in the Curtiss aeroplane factory during October, 1911, and found its first application in revealing the streamlines about the wings and body of a small model of the new hydro-aeroplane. The wind-tube, which is but the model of a full-sized wind-tunnel to be •built later, is shown in the photograph. It measures six feet hi length by fifteen inches square in cross-section, and is provided with a glass door through which models can be introduced and studied in the air stream. As usual the current of air is generated by an electric motor driving a suction fan or screw at one end of the tube, while at the other end is inserted a honeycomb structure for causing the air to flow in straight lines free from swirls and eddies. The “honeycomb” in this case is a standard aeroplane radiator having cells four inches long by one-fourth inch square in cross-section. The air enters the tube through this straightener at a part of the room free from obstructions and well above the floor. As a consequence it moves in a smooth current of uniform velocity. A fine silk thread suspended in the current shows -a deviation of the stream-lines of but a small fraction of a degree to and fro from exact parallelism with the walls of the tube. The speed of the air, tested when the motor was not perfectly steady, showed a diminution of nearly two per cent across the tube at the middle of the window, when explored from mid section to within less than two inches of the walls; but in the stratum extending from the walls inwardly 1.5 inch, a considerable variation of wind speed was observable, due no doubt to skin friction on the four feet of wall between the radiator and the section in question. A cone was placed at the motor end of the tube to incase the 30-inch suction screw, and a like cone may be placed • before the radiator, if thought advisable, to improve the flow of air. This wind-tube is so simple and effective that it may be found serviceable to other aviation students who may wish to make like experiments. But of course it is desirable to have very much larger tubes, equipped with proportionately large radiators, since a small model may easily disturb the stream-lines as far as the walls of a small tube, and thus give different indications from those for freely flowing air. The radiator not only makes an efficient straightener, but also may serve to keep the air at any desired temperature, if a suitable fluid be made to course through it. This remark applies particularly to a wind-tube having • a closed circulation of air. Two methods are used by Mr. Curtiss to delineate the stream-lines of the air current flowing past any model inside the wind-tube. One is to attach a fine silk thread to a fine wire, and hold it at various points about the model; the {Continued on page 565.) The Strength of an Aeroplane (Concluded from page 551;) other is to allow streams of smoke to flow past the model. Both methods show the direction of flow at all parts of the current except where the eddies are so violent as to make the thread flutter and the smoke streams break and lose their identity. The thread is more convenient to use than the smoke, but if too long will not accurately coincide with the stream-line, owing to the effect of tension. The smoke coincides with the direction of flow at all points, and, as Prof. Marey has shown, may even indicate the velocity at all parts of the current, if the smoke-streams be emitted from nozzles vibrating at a known rate transversely to the current. In this case the smoke streams are wavy. and show by the number of waves per inch what is the speed of the current at the place of observation. The number of waves per inch can easily be counted on -a photograph of the model and of the smoke-streams surrounding it. Indeed, the velocity and direction of flow for an entire longitudinal section of the current about the model may be realized by a glance at the photograph if the smoke streams surrounding it. Indeed, the comb placed transversely to the current and vibrated lengthwise, say ten times per second, as done by Marey. Mr. Curtiss is at present trying different methods of producing distinct and clearly visible lines of smoke. At first air was sucked over the surface of ammonia in a bottle, thence over hydrochloric acid in a second bottle, thence through holes in a tube placed across the wind current. But the smoke so produced is pale and requires good lighting in a dark wind-tube to render it distinct enough for easy observation and photography. It is hoped that a simple method may be found whereby dense black smoke streams may easily be produced and led into the current. The absolute velocity of the air in the Curtiss wind-tube was found by a screw anemometer to be about 25 miles per hour at the middle of the current. The relative velocity at different parts of a section of the current was found by observing the deflection produced on a straight exploring wire, like a knitting needle, ten inches long, suspended from a horizontal wire fixed transversely to the stream. When the point of suspension of the exploring wire was moved across the tube, the suspended wire was deflected from the vertical less and less as it advanced from the mid section toward the lateral wall. The impact pressure of the air against the wire is proportional to its displacement along any longitudinal line of the current. Hence, of course, the velocity is as the square root of such displacement. In this manner the speed of 'the current was observed to decline about two per rent from midstream to within two inches of the lateral wall, as previously stated. The wind-tube and tension tongs described in this article were designed by Mr. Curtiss and Dr. Zahm, who were experimenting together. Two other contrivances were devised for finding the tension in aeroplane wires; one being an instrument for giving the pitch of the wire in vibration, the other being an ln- If you depend on the horse-and-wagon system of delivery, let us show you in dollars and cents what International Commercial Cars have done for others. They will do the same for you. If you own big motor trucks, let us show you how an International will save time, fuel, oil, and wear by doing all your light hauling. International Commercial Cars have a place in every business where prompt and efficient service is necessary. The man who uses big trucks for his heavy hauling should buy Internationals for the lighter work—making quicker trips, more prompt jeliveries, and increasing the efficiency of his delivery service. 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Let us send you our literature. Trussed Concrete Steel Co. 402 Tn»»ed Concrete Bldg., Detroit, Mich, strument for showing the lateral displacement of the wire by a given foroe, from which the tension could be read in a reference table or along a specially designed index scale. Some Locomotive Curiosities (Concluded from page 569.) were connected by crossed rods as will be understood by examining the illustration. This engine never did practical work. It was jacked up clear of the ground and tried under steam in January, 1856, at Kew, near London, where it was sharply criticized by' some engineers. The writer saw it in the early sixties when it was fast rusting away in the stable yard of an inu near Kew Bridge. Double piston balanced locomotives were patented by Bodmer in 1834, and some engines were built for English railways in 1842. The rod of one piston worked within the hollow rod of the other and they were connected- to oppositely disposed cranks, which were four in number. As the mechanism was internal and the appearance of the engines differed in no wise from the ordinary locomotives of the day, they are not illustrated here. The next remarkable locomotive selected is illustrated in Fig. 6. This engine was a partial repetition of the “Hurricane” (Fig. 2) for the boiler and running gear were on separate frames. It was designed for the Philadelphia and Reading railroad by G. W. Nicholls and was put to work in 1847. This engine was appropriately named “Novelty.” The cylinders were 18 inches in diameter by' 20 inches stroke. Driving wheels 3 feet 10 inches in diameter. The weight of the engine proper was 21 tons, and the frame carried a cylindrical iron water tank which had the appearance of a boiler.' This was used as a condenser and' feed water heater, while ' the boiler was carried on a separate frame behind the engine. This, in turn was coupled to a tender which does not appear in the illustration. The boiler had return flues and burned anthracite coal; it had a total heating surface of 1,085 square feet. The fire was urged by a fan placed in the cab. The condenser tank was surmounted by a large smoke stack, but as nothing passed through the latter save the surplus exhaust steam from the condenser it was apparently placed there merely for appearance. Steam was carried from the boiler to the engine by a jointed pipe. This engine hauled coal trains of 750 tons at 10 miles an hour. This complicated piece of machinery only worked for a short time. Complicated machinery is not, in itself, objectionable, and when complication enables a necessary function to be better performed it is allowable; but one can scarcely see how such a machine as is illustrated in Fig. 8 could have been seriously considered in the light of modern practice. Nevertheless, this engine was built in 1881, and ran on the Canada Southern Railway. It was designed- by Eugene Fontaine. The cylinders were 16 inches diameter by 24 inches stroke. The engine weighed about 40 tons. The driving wheels were 6 feet in diameter, having frictional contact with wheels 4 feet 8 inches in diameter, which were. integral with wheels 5 feet 10 inches in diameter running on the rails. In other words, instead of pro-pulson by power applied directly to the rails as in the common locomotive, two extra wheels were interposed to effect the same result. The “Fontaine” was a fast engine, for it drew two coaches 111 miles in 98 minutes, but many ordinary locomotives traveled faster with heavier loads. Geared engines were tried as far back as 1838, but it was then found that a gain in speed meant a loss of power, and as locomotives are required to haul loads, these engines were short lived. The “Fontaine” engine was not original, as the same arrangement was patented in England by Johnson in 1848. The foregoing notes will, perhaps, give a good illustration of the adage that “History shows us what to avoid." Caryl Davis Haskins CARYL DAVIS HASKINS, one of the best known electrical men of this country, died Saturday morning, November 18th, in Salt Lake City. Mr. Haskins The Technique of Clam Digging It has a technique and it is not easily learned. There is a certain way of handling the boat, of pushing the rake with its absurdly long handle into the water, of scraping the clams into it, of raising the rake—why there is as much technique about it as there is in playing a piano. You may debate with a disputatious person if it is more useful. Probably there isn't any book on the technique of clam digging and there isn't a periodical devoted to it exclusively. If there was a new development in the technique of clam digging, the Scientific American would record it, as it did the development of the steam oyster dredge and ever so many other things, including those departments of science which have their own technical publications for specialists in them. The' Scientific American covers the whole field, but it confines itself to the important things, those which affect the life of a who'.e people, rather than those which affect only a few individuals. What it really does is to give the news of civilization. It has been doing that for sixty-seven years. It is doing it now better than ever it did, on a bigger, broader scale. It is growing and widening as science is developing, and always it maintains its authority. See Correspondence Column, Page 564. The test of a magazine's merit is that its readers tell their friends about it. We recently asked our subscribers to send us the names of those whom they believed the Scientific American would interest, and we are gratified to find that so many of our subscribers believe that its merits will appeal to such a large number of their friends. Have you sent a list? If not, Here is the way: Simply send us the names and addresses of the people whom you think will be interested and we will do the rest. An accurate record of all names received in this manner will be kept, and for each new subscription we get from any list we will extend the subscription of the person who sent us the list for four months. Thus if we receive three new subscriptions from any one list the subscription of the person who sent us the list will be extended for a full year. Of course you may send as many names as you wish, the greater the number of names you send the larger the number of subscriptions we will probably receive and the longer the period for which your own subscription will be renewed.' Be careful to write the names and addresses plainly and don't fail to put your own name and the address at which you are receiving the Scientific American on each list you send. Address all lists to Circulation Department, Scientific American, 361 Broadway, New York. strument for showing the lateral displacement of the wire by a given foroe, from which the tension could be read in a reference table or along a specially designed index scale.