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Water Propellers for Ships To the Editor of the Scientific American: I observe in Scientific American of September 21st— the most interesting and instructive paper that as I think now exists—you mention under the heading of “Auxilty Sailing Schooners” the suggestion that they should be equipped with auxiliy engines. Will you permit me to suggest that it might be worth the consideration of the owners of such vessels, whether they might not advantageously adopt the water propeller. Your readers will no doubt be aware that the water propeller has great advantages over the screw in regard to economy, as its action on the ship takes immediate effect, and there is none of that waste through the screw requiring to be revolved up to the then speed of the vessel before the auxiliary takes effect. The water propeller was tried during the sixties, probably in the year The only fair trial that it had, as I thought at the time, was in the case of three gunboats, the “"Vixen,"' “Viper” and “Waterwitch.” The vessels were, I believe, identical in form and in power exerted. “Vixen” and “Viper” were screws, the “Waterwitch” had the water propeller. The result showed that there was practically no difference in speed; and it should be remembered that no sufficient trials were ever made to ascertain the best position and mode of exit of the water. The handiness of this propeller for starting ahead, stopping, and going astern was greatly superior. The trouble with the screw having to be feathered is avoided. The motion of the centrifugal pumping engine; acting like a great gyroscope, tended to steady the ship. I should add that a rough estimate was made, when © 1912 SCIENTIFIC AMERICAN, INC Non-astringent Persimmons To the Editor of the Scientific American: In the issue of October 26th of the Scientific American I notice an article on “Non-astringent Persimmons.” In this connection I wish to state that I have bought at fruit stands in a number of Florida towns, du^ng a number of years past, a variety of Japanese pere^^on locally known as “apple persimmon,” which is so caled on account of the fact that, when taken from the tree, this particular variety is free of al tendency to pucker, and can be eaten at once just as would an apple. When picked ripe, it is ^rn and fully colored, good flavored and sweet, and decidedly pleasant to the taste. When bitten, the bite comes out with a crisp snap. I at one time lived next door to a man who grew some of this variety of persimmons in his yard, and know that they were treated in no way to give them the qualities mentioned. E. W. Price. Tampa, Fla. C^ents To the Editor of the Scientific American: About the time the “Titanic” was sunk, I read an article in your paper in which the Labrador current was alluded to in terms which seemed to indicate that its cause or origin was obscure or unknown. ooking the matter up in several encyclopredias since, I find that there is an almost total lack of definite information as to any of the ocean currents, including the Gulf Stream. For many years I have had the idea that tho Gulf Stream, as well as the ocean currents of the eastern hemisphere, were the result of the inertia of the waters of the oceans against tho rotation of the earth, piling up enormous masses of water against the eastern shores' of both hemispheres, and flowing away on lines of least resistance. A casual study of the streams from this viewpoint will, I am' sure, make my idea perfectly plain, and, considered in connection with the heat at the equator and the cold at the poles, provide an accurate dete^nination of the source, direction, and effect of every current in the seas. This idea may not be new, for, as stated above, I have heldit fora long time, but certainly such sources of information as have been available to me recently do not convey any definite idea of the causes. If there is any novelty or value in this suggestion, please give it to your readers; otherwise, please destroy this letter and ^rndly direct me to some suitable writings on the subject. Richard At Magill, Atlanta) Ga. Solving the C^btmas Gift Problem A LARGE manufacturer recently wrote us as follows : "We send out Christmas presents to some” of our customers. Suppose we sent you from twenty to fifty subscriptions, what is the lowest price you could make us." We replied to our correspondent's letter and quoted a s^^ial price. The following extract tells the story. "Go ahead and have one hundred and fitfy cards printed reading as follows : Our correspondent is not only saved the worry and bother of attending to the details of having the gifts delivered- at the proper time, but the arrival of the SCIENTIFIC American each week during the year serves to recall to the minds of the recipients pleasant memories of the donor. If it is your practice to give Christmas presents to your customers or employees, a year's subscription for SCIENTIFIC American, or a copy of the “Scientific American Reference Book,” or better still, both in combination, makes an ideal gift, that is of permanent value to the recipient. A Promise Unfulfilled To the Editor of the Scientific American: I cannot help from feeling that it is my duty to express myself along the lines of thought you conveyed so accurately to the scientific and lite world in your paper published September 21st, 1912. This subject, “A Promise Unfulfiled,” dealing with America's dow advancement in aero-navigation, is a seririous subject, and the causes are just as you say, “More national than individual. “ I have always thought that large or good-sized cities were the places to organize and get money for this work. This may be so in the North, but it not been so in this part of the South, and to ilustrate to you that what I say is true, the following outline should be convincing : A little over two years ago two men started actual work on this subject in. one-part of this city. About the same time .two other men started work along the same subject in brother part of the city. ' Now, lam in a'posi- tion to know that not a single man of the four had any intention Of buil^ng a fl^ng machine, jumping; into it, and fl^ng off, as 'tis the dream of so many people; for they al knew that expe^menting, studying, and hard work were necessary first. There was little capital available among the four men, but by two men devoting their entire time .and urang to good advantage the little money they -flying models and gliders were constructed; : - later the experimenters consolidated, and machines were constructed. One machine was fitted up with a jI) horse-power Buick motor, and with this ^^hine the men made use of such experiences as they could get traveling and falling around on the ground. No attempt was me to fly, and “Why not?” was explained to a.-nwher of people. Soon the ,.time»oame to do more. Large, up-to-date machines were ^^trueted of the best material and workmanship. available (foUowing plans obtained from a northern concern). To install - in one of these mac^rnes a cheap motor would have been foolish, and to buy a good motor the sum of $225 more than what they ha on hand was necessary. They tried to raise this amount here. Every poor man and rich' man was cornered; they had material on hand worth four $225, and this was offered for collateral but they were still unable to raise the required sum here. I will say, just here, that tils city has about forty thousand inhabitants, a number of whom are of considerable wealth; it is a city of self-pride and enthusiasm; and a boaster of its place in history. No one was asked to give the money away, but nevertheless on no condition could the $225 be obtained for the purpose of experiments in aero-navigation. About 21 miles from this city there lies a little town of about four thousand people, that is called by some people here a country town^. ^^ardless of what it is called, right in. the town of Gastonia, N. C., they obtained the $225 and a little more to carry on their work. A $1,!20 Maxi motor was ordered at once. What America needs along the line of preparing a machine or scientific article for the market is a little more of the German spirit. He organizes a company first for the purpose of experimenting with the articles. The Gernans have confidence in what they are doing, they ex^^t results, and they get good results. This nation as a whole tries to get rich too quick. Whiten you comp this nation's strength in aviation to that of a single foreign nation, by representing that foreign nation's strength as the largest flying ^^chine, and this nation's strength as a tiny butterfly, every true- born American should fell ashamed. Flying mac^rnes may seem foolish to a lot of people; but when one ^ads in the daily newspapers of what the machines have done in time of war, one should stop to think what this nation could do in time of war. They should know that most of the foreign countries are prepared to fight with the help of air scouts, while we are not. Patience and a little more confidence wiU b^ng results, especially in a country which is the birthplace of the men who traveled long and hard roads to give this nation as well as to the rest of a world a concrete foundation on which rests the successful flying machine. Charlotte, N. C. A. M. WEBB. Automobile Toll ^rads To the Editor of the Scientific American: If charters were granted by States to corporations for the purpose of building important State and interstate roads for the exclusive use of rubber-tired motor-. driven vehicles, the plan would, I believe, be the best way to secure a good many economically built and carefully kept roads. For such a road to pay dividends it would have to have easy grades and as smooth a surface as could be possibly maintained. Such a road would make possible the use of cheap automobiles, which would be used in great numbers if only proper roads were built for them. The corporation could keep motor buses and trucks for hauling passengers and freight on such roads for the benefit of the public as well as the corporation, all vehicles to have the same rights on the road. All vehicles being rubber tired and motor driven would probably not be so wearing on the road as where rubber-tired and iron-tired vehicles are used on the same road Such a road should not cross public highways at the same level, but go over or under them, not only for safety but also for the purpose of easy collection of tolls. Tolls could be collected in this manner: station agents could be kept at intervals of from four to six miles along the road, where automobiles could be allowed to go on or off the road. Parties taking an automobile on a road at a station would have to purchase a ticket, and when aarvnig at the station which the ticket called for, they would have to deliver the ticket and the agent would permit them to leave the road. In support of the automobile toll road idea I will refer to the great railroad systems of this country; how they have contributed so much to the development of the country under corporation management; how competition has stimulated inventions that have improved and cheapened transportation. The same thing would happen if automobile toU roads were constructed and managed by corporations. Efficient work ' would be done in construction and maintenance; competition would stimulate experiment and invention, and the result would be of great benefit without in any way interfering with present public roads, but rather stimulating the building and improving of them. No considerable number of citizens would care to advooate public ownership of railways ; the only general desire has been for some form of just regulation. This being - the case, why not have automobile toll roads, built by corporations, between important cities and towns, instead of having such roads built in a haphazard way by counties, at great cost and with no provisions for maintenance. Stenberry, Mo. Clifton R. Summers. The Gyr^opk Torque of a Rotating y To the Editor of the Scientific American: Apropos of Sir Hiram Maxim's suggestion, in your issue of October 26th, to determine by a special research the gyroscopic torque of a rotating body, permit me to say that the required value of the torque can be found by use of the simple method and well-known formula published in the Scientific American Supplement for March 2nd, 1912. Sir Hiram's proposed apparatus should, of course, yield correct results; but since these can be accurately foretold by computation, the suggested research would at best merely verify a well-established and very reliable theorem in mechanics. Every engineering student learns how to find the moment of inertia of a body, say of a propeller with reference to its axis. Multiplying this quantity by the speed of rotation times the speed of deviation of axial direction gives the required gyroscopic torque. Thus, starting with a familiar physical quantity, the required torque is found by simple arithmetic. But, though the computation is so easy, the amateur may very well engage for a few moments some competent person to teach him to perform it correctly. After that he can figure the gyroscopic force of his rotating parts with entire satisfaction, and make a olear estimate of its disturbing effect. Washington, D. C. A. F. ZaBm
