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The Bow Rudder To the Editor of the SCIENTIFIC AMERICAN : Your issue of March 15th is just received here to-day, and shows a desultory interest in the bow rudder. I spent last summer on the Lake of Thun, and noticed that the fleet of seven steamers were all fitted with bow rudders. The wheel house contained- two wheels, mounted one immediately abaft the other, their relative positions, fore and aft, denoting which rudder they controlled. These ships were legitimate river or lake steamers, not double-ended ferryboats, and were steered by the after rudder, on the lake. At Interlaken is a long canal into which the steamers ran forward. They were always backed down to the lake, and during that operation were steered by the forward rudder, which temporarily represented the stern. At Thun, where the lake empties and where the current is strong, the steamers are turned out in the lake. and entered stern first, again using the bow rudder. At Thun there are two landings, in making one of which both rudders are used, a quartermaster for either wheel. This operation seemed to give a decided sidewise or broadside motion, which may have been the reason for it, the current past the landing stage being rapid. Paris, France. WILLIAM H. BRADFORD. Automatic Lighting of Light Buoys by Means of Selenium To the Editor of the SCIENTIFIC AMERICAN: An article in your issue of March 8th, entitled Lighting Light Buoys by Wireless, is read with great interest, and the new application of the fniliar Wireless distant control appears to be an improvement in this case over the old system of shore control of lights on buoys. In practice, however, it wiU doubtless be found that additional complication is involved and a certain degree of reliability sacrificed; also the instalment of wireless tuning and receptive devices in buoys will be an additional expense which not meet with favor. If it is the object to avoid the old system of shore supply and control to light buoys and further locate the source of power in the buoy itself and do away with the cable, the writer suggests that the buoy contain the necessary batteries, also a selenium cell and relay. By this method we do away with not only the cable, but also with the proposed wireless apparatus, and have a purely automatic sivnl which wiil need occar sional renewals and inspection. It seems hardly possible that this application of the selenium cell is new; but since it appears a simplification of the newly proposed Gmn system, and since no mention of it is found, this idea is respectfully submitted and may be taken for what It is worth in the estimation of those familiar with the light-buoy problems. The above system is, of course, applicable to many modification for example, control by of a ship or shore searchlight. A. KELLOGG SLOAN. Brooklyn, N. Y. Undamped vs. Damped Oscillations To the Editor of the SCIENTIFIC AMEBIC AN: My attention has been called to certain publications that have been made in your Journal of late in which the statement has been made that the result of the Navy test on radio-telegraphy, as conducted between the Arlington station and the cruiser Salem, had shown very conclusively a marked superiority, in long-distance operation, of the undamped oscillations over the damped oscillations or, as it has generally been spoken of in the press in discussing these tests, of the oscillations from an arc generator as contrasted with those of a sparkgenerator. While it is perfectly true that superior results, for given amounts of energy, were secured with the undamped oscillations, over those secured with the damped oscillations, the real cause of this superiority has not, I believe, as yet been noted in any of the press statements. I therefore wish to call your attention to the fact that this superiority was shown when using the Fessenden receiving apparatus supplied to the cruiser Salem as part of its equipment in connection with the spark equipment supplied by the National Electric Signaling Company. It was a fact well recognized by the engineers of the company that the heterodyne would work to its best advantage with undamped oscillations, it having been invented and developed for that specific purpose and later adapted to the spark type as well, and it was also well known by them that it supplied the best known receiving mechanism for undamped oscillations. This superiority was so great that after the first few days all other forms of receiving apparatus were abandoned by the Navy officials in their test with the undamped oscillations. The heterodyne receiving apparatus operates upon the principle of beats in which interference beats of adjustable frequency are produced between the incoming oscillations and those produced in a local circuit. It is thus possible, in view of the action being a resultant of two forces, one from the sending station, and one produced locally, to considerably increase the energy available for operating indicating mechanism for receiving the signals. It is also possible by adjustments at the local circuit to secure a pure flute-like musical tone of any desired pitch and thus allow the operator to select what best suits his ear. This note is written simply in the interest of accuracy in order that readers interested in this line of work may be made aware of the real cause of the superiority shown by the Government test. Pittsburgh, Pa. SAMUEL M. KINTNEB. Submarine Mountains To the Editor of the SCIENTIFIC AMERICAN: It may be of interest to some of the readers of the S CIE NTIFIC AMERICAN to know that there are mountains and volcanoes under the sea, the same as on the surface, one of which I will describe. While acting as second officer of the U. S. cable ship Liscum, stationed at Manila, P. I., we were ordered to proceed to Malabang, and run'a line of soundings from that place to Zamboanga. Tese are two important military settlements on the island of Mindanao, and it was the intention of the department to run a new cable between these two places. After leaving Malabang we steamed slowly toward Zamboanga, taking soundings every thirty minutes, keeping a record of same. The water gradually deepened from the time we left Malabang until we were off Lutan-gang Point, where we got 800 fathoms, when the man in the crow's nest sang out Shoal ahead. We immediately took bearings and fixed the ship's position on the chart, but did not see anything marked on the chart that resembled a shoal or anything like it, so we slowed down and proceeded, stationing a man at the lead, and when directly over the shoal spot we got six fathoms up and down from the bridge. It appeared to be a circular spot about 100 feet in diameter and of coral formation. We only got one cast of the lead when we were in deep water again, so we came to the conclusion that we had run over either a submarine volcano or mountain, for nothing short of a good-sized mountain or some other kind of submarine formation could give such soundings in two or three feet, as sounding a few minutes before we arrived over the shoal spot gave 00 fathoms taken with the patent sounding machine. Cape May Point, N. J. ALBERT E. REDIFER. Ignition Devices To the Editor of the SCIENTIFIC AMERICAN : The writer, a reader of the SCIENTIFIC AMERICAN for many years, has noted with interest the article, Small Inteal Combustion Engines on Land and Water, in the April 5th number. The fifth paragraph in this article would lead one to believe that the high-tension magneto was the best ignition for stationary and marine engines and offered a complete solution for their ignition troubles. You may be interested in knowing that from careful investigation, we find only about 40 per cent of the stationary and marine engines now being made are equipped with jump spark (high-tension) ignition, this including both battery and magneto. If engines already in service are counted, the make and break engines outnumber the jump spark three to one. As your correspondent is no doubt aware, the principal reason for the adoption of the high-tension magneto on the automobile was the difficulty in timing four make-and-break igniters to operate in correct relation with each other and a common source of current. This objection does not hold good with a single-cylinder engine, which represents by far the majority of power units in the stationary and marine field. As to the comparative efficiency, from a purely igniting standpoint, there can be no question but that the make-and-break is far the superior. The spark is more dynamic in character, and is hotter. The make-and-break system is most successfully used in connection with low-grade oils and gas-producer units, where the ordinary high-teion, jump-spark plugs rapidly short circuit by deposits of soot. The most simple ignition device imaginable is a low-tension engine-timed alternating-current magneto. This machine has no commutator and brushes, no timer contacts like the high-tension magneto; it has a single winding on the armature, requires no coil, switch or other auxiliary apparatus, is built into the engine, thereby forming a part of same, and eliminates entirely the complications of battery or high-tension magneto ignition, and at the same time furnishes a vigorous spark suitable for igniting all kinds of low-grade fuels. We can cite to you several instances where, since the advent of this type of magneto, manufacturers have abandoned the jump-spark system and gone back to the make-and-break. This is especially true on single-cylinder engines where the high-tension system has absolutely no advantage and, in fact, has several drawbacks. Of course, where there are a number of cylinders, the cost of the make-and-break igniter mechanism would be greater than the jump-spark magneto and plugs. We believe after exhaustive investigation that it is the source of ignition that will eliminate the ignition problem in stationary and marine units. The high-tension jump spark has its field, but this field is certainly not in connection with small internal combustion engines, for many reasons. H. R. VAN DEVENTER. Sumter, S. C. Straightening the Mississippi River To the Editor of the SCIENTIFIC AMERICAN: Notwithstanding all that has been written by correspondents in the SCIENTIFIC AMERICAN opposing the policy of straightening the course of the Mississippi River, I feel confident that"this method, together with a system of levees as advocated by the SCIENTIFIC AMERICAN, is the most practical of all the suggestions yet made. The actual distance from Cairo to the Gulf is about one half the present length of the channel from Cairo to the mouth of the river. If this channel should be straightened to two thirds its present length, the pitch per mile and the consequent flow in miles per hour would be increased one half. The product of these factors gives us a theoretical capacity of discharge to the Gulf equal to two and one quarter times that at present. I am fully aware of the fact that theory and actual practice are often separated by real, or seemingly impractical, barriers. Great obstacles are, however, often overcome by Nature herself when directed by human skill, which in the present case may doubtless be applied so as to make the force of the current do the bulk of earth removal. For instance, a loop of the river may be cut out by digging a deep, straight and narrow channel through the alluvial soil to start the current, and if necessary may be further aided by building booms, coffer dams, etc. This straightening of the course of the flood channel would surely be a long, grual, and expensive engineering feat, but it would accomplish results for the lower Mississippi region far more effective than the reservoir schemes. However, I believe that much of the real lowland should be allowed to be overflowed at each flood season. Scranton, Pa. CHARLES H. FOGGETT. Control of the Mississippi To the Editor of the SCIENTIFIC AMERICAN: I have read with considerable interest the letters that have been sent in on the flood problem. As the editor of the Boot and Shoe ecorder remarked in the May 3rd number, I am an amateur, but I hope I can see a little farther than some. i I will agree with Danville, Ind., on the reservoir proposition. Suppose there were a half dozen reservoirs in the Mississippi valley, where would the surplus water go in a flood like the one we had in this country in March? It would be all right if it rained only a few miles on each side of the river; then reservoirs would hold the dampness; but when the Mississippi drains one half--or nearly so-- of the United States it is quite different. White Plains, N. Y., thinks that a dam every few miles on the Mississippi would cost only a few dollars. The channel would be in a fine shape with his dams. The old river would be one long string of rapids, which would benefit no one. And again, suppose the dams were there, would that keep the flood in the channel? No! Littleton, Del., says it would be a snap to straighten the Mississippi. Yes, it could be done, but what good would it do? Say it is as straight as a string from St. Paul to the Gulf and wide and deep enough to carry the highest floods. How long would it stay straight? Until the first high flood came, or may be a couple of years, which I doubt. Why? Because on one side the bank would cave or a pocket would form. That would have a tendency to form a cross current, and slamming up against the other bank, out would go another pocket. So in a few years it would be as crooked, if not more so, than it is now. We will suppose again that the whole river flowed in a channel of rock. Littleton, Del., would be in the swim. Who ever heard of a runway for a flood? The Secretary of the Interior must have been thinking of muskrats or beavers, as these animals use runways. Plattsburg Barracks, N. Y., should know that there is a slight difference between the Kaw River at Kansas City and the Mississippi. He asks if the channels of certain rivers have not been choked? The Kaw might have choked in 1904, but that is ancient history. He should keep up with the times. Everyone knows, or should know, that bridge abutments retard a river ever so little. Bridges go out only when houses and buildings form a dam, and then something has to .go. It seems to me that dykes and revetting would be the best. It doesn't look fair to tax the land that abuts a river and not the plantation or farm back of it. If I lived five or more miles from a dyke I should be taxed to keep that dyke up. Then they would be built larger and better. I have no fool suggestions to give, as there have been too ny of that kind sent in. Thornville, Ohio. JAKE HITE.
