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Panama Canal Problem in 1638 To the Editor of the SCIENTIFIC AMERICAN . When was a Panama canal first thought of and discussed ? It must be a very long time ago, because I have just been looking through a very old and very interesting book of mine on commerce, published in 1638. It gives a map of each continent as then known, and mentions with particulars of each all the towns available for commerce in each. The map and descriptions of the towns in America are naturally rather primitive, but the following paragraph occurs with reference to Central America and is, I think, of special interest at the present time: Peruana contains the southern part of America, and is tied to Mexicana by the Straight of Darien, being 10 miles broad; some hold the Spainards did once intend to cut this straight through and make it navigable, and thereby shorten the way to the South Sea, China, Molluccos, but hitherto we have not heard that the same is any way attempted. I thought your readers might be interested in this extract. H. ALLAN MORGAN. Holm wood, Knutsford, Cheshire. Electricity as a Factor in Plant Growth To the Editor of the SCIENTIFIC AMERICAN: Prom time to time reports have gone out as to the effects of electricity on the growth of plants. Nearly all of these effects are alleged to have been observed in close proximity to lines carrying heavy currents, but as yet little has been done ip the line of observing the effects of this all-pervading but mysterious force. It is possible and probable that electricity will yet be found to play an important part in the growth of vegetation; and who can tell but what, when it is once understood, we shall see it working as great wonders along this line as it has along others. As an instance of the room there is for the study of electricity as it affects plant growth, I shall relate an experiment I performed the past summer. I had noticed that nearly all weeds are well provided with points. I also noticed that such plants as sugar beets, cabbages, etc., that are not provided with points, are affected by the close proximity of weeds to an extent out of all proportion to the amount of fertility the weeds would rob them of, and they are much more seriously affected by the weeds than are other plants that are provided with points. Now it is a well-known fact that the atmosphere is charged with electricity, and that electricity is most readily taken up by points. I went ahead on the supposition that plants take from the air the electricity it is charged with, and that in some way this electricity is necessary for their best growth. I supposed that the unusually bad effect of weeds on smooth-leaved plants might be due in a measure to the electricity the weeds robbed the other plants of. In order to test my theory, I selected a sugar beet and a cabbage and kept them well cultivated, but set up among the foliage a number of wires with sharpened points and left them there during the season. The result was that these plants showed a much smaller growth than others not so treated. So far the experiment seems to have borne out my supposition that electricity does materially affect the growth of plants, and that the points on plants are important agents in gathering this force. If on further investigation this supposed law holds good, it would play an important part in the selection of varieties best suited to avail themselves of the electric energy. There are many things about plant growth and soils that are but meagerly understood, and this field would seem to be one of the most interesting and profitable for scientific study. Almena, Wis. R. E. DIMICK. Ideal Automatic Train Control To the Editor of the SCIENTIFIC AMERICAN: Much valuable space has been given of late in your publications as well as others to the problem of automatic train control. For more than twenty years inventors have been working on this problem, and all along the same lines, that is to say, they try to provide means whereby a locomotive will be arrested automatically should it pass a signal set at danger. The inventors have been working along this line because the heads of railways concluded that these disastrous accidents are due to the locomotive passing a signal set at danger. As in every other problem, the cause must be first found before the remedy can be applied. The inventors took the fact that "the locomotive passes a signal set at danger " as the cause. This is true; but why not investigate, and find the cause for the disobedience of a signal set at danger? One of the railroads, about which there has been much discussion of late, gave out "specifications" setting forth the different characteristics which they expect an automatic train control to possess before they will consider the adoption of the same. Let me point ov>t in this connection that even if this railroad compan should find a system that will do all those feats set forth in its "specifications," this railroad company will be greatly disappointed if some time after the installation of such a system they should read in the "extras": "Big railroad wreck. Forty killed." Let me point out now that a system that will arrest a locomotive only on passing a signal set at danger, might at times protect the trains and at other times it will not and the chances are just as much one way as they are the other. Assuming a "block" to be a mile long and a train stalled at the end of this block, and assuming further that the mechanism operating the roadside device is in good condition, then any locomotive passing this roadside device, which was set to danger by the stalled train, will be arrested and brought to stop in time enough to protect both trains. The same thing will happen if there should be a broken rail near the end of the block. But all this assumes "ideal" conditions, i. e., all obstacles at or near the end of the block, and the fact that these obstacles can just as well be at the beginning of the block is ignored. No system, such as outlined above, could ever protect a train if the train be stalled 200 or 300 feet from the beginning of the block; nor could it protect the oncoming train if there be a broken rail within 200 or even 500 feet from the beginning of the block. I do not think that a roadside device could be designed which would have a greater operating efficiency than the present-day automatic signals. Yet, perfect as these signals are, they do fail at times; and as perfect as such a roadside device may be, it will fail at times for the same reasons that the signals fail. The roadside device might be operated independently of the signal, yet it is possible for the track relay in both of the circuits to stick. Track relays often remain energized by stray currents, which act the same as though the block occupied by a train were clear, and the track relay for the roadside device would not be exempt from such a condition. There are many other conditions that have not been considered in the search for an "ideal automatic train control," and in which cases a train control, such as outlined above, would prove useless. Thus it will be seen that the steps taken so far to solve this important problem are not altogether the right ones, and the solution lies elsewhere, but it does exist, and I know it will come. MAXIMILIAN WEIS. The Real Problem of the Mississippi To the Editor of the SCIENTIFIC AMERICAN : The question of protection of the Mississippi River bottoms from overflow and the matter of canalization of the river from various points has been discussed in documents, which some of the debaters on these questions may not have read. The idea of building reservoirs on the headwaters of the Mississippi, for example, was put into one of the first of the many studies of the hydraulics of the great river by Mr. Charles Ellet, who afterward won renown as a fighting man during the civil war. The classic report of Capt. A. A. Humphreys and Lieut. H. L. Abbot submitted to the Bureau of Topographical Engineers of the War Department in 1861 is, of course, the original source of much information on the Mississippi. The abbreviated "Levee System," is, perhaps, the more familiar edition of this report. The report very clearly and apparently irrefutably exploded many of the theories which to this day crop up in any argument--the reservoir notion, for example. The army officers, after the manner of their kind, collated everything that had been discovered about the Mississippi and its tributaries. They even gave the then meager rainfall records from the far and scattered forts on the westward slope of the river basin, for instance--those forts where army men, in the lonely routine of their daily lives, turned from the parade grounds to study birds and mammals and the lay of the land, enriching the literature of natural history-- for instance, Capt. Bendire and Dr. Elliot Coues. James B. Eads was tile one, who after the civil war led in the combat against the Mississippi. His distinguished service led the SCIENTIFIC AMERICAN to propose that he be made president, and if he had been made president, the Mississippi River problem would not now be the brain teaser of all the solvers of the "How Old is Ann?" question. The trouble with the Mississippi is that it fills up its channel with sediment, and the Government keeps right on building up the levees, till they are as high as the platform of the gallows of Haman, upon which they cut from under, and leave some people literally hanging to the grapevines. Mr. Eads said in effect that the levees should be built out from the highlands on the east and west side of the river valley perpendicular to the river channel. Then the overflow would be "eddied" and the sediment deposited among the trees. I have seen in a caving bank, and in a hollow tree places where sediment deposits were twenty feet deep-- this in eddies of old. The purpose of the eddies, in pools made by earth dams across the bottom, perpendicular to the flow of the river, would be twofold; first, to build up the bottoms lands; second, to make the current swift enough to scour out its own bed, and carry the sediment till it swung out into the eddies out of the channel or on to the Gulf. Incidentally, the dams would serve as refuges. That is to say, the greatest and till then the only thoroughly equipped student of the Mississippi solved the problem upward of forty years ago; but so perverse are the gentlemen who take levee contracts, and so conservative are the gentlemen who have the power. that the obvious remedy and, so far as any one has ever discovered, the only remedy has never been applied, except when the river itself roars through that tremendous folly--the levee system as built in recent years. I have not the figures here, but I question whether the floods last year were as great in volume as the previous floods--those of 1844, or of the early SO's. I would suggest as food for reflection the fact that the streets of New Madrid were overflowed last spring for the first time; measurements of the river surveyors show that in four or five years the river channel in front of New Madrid filled in more than five feet. Below New Orleans it filled in nine or ten feet. No wonder that levees, with only a margin of a few inches, or eighteen inches, fail to hold when the place where the current is swiftest is deprived of a depth of five feet of freeway. Those who desire to verify these statements may do so by referring to the Report on Survey of Mississippi River, Document No. 50, of the House of Representatives, Sixty-first Congress, first session, and to the reports of the Mississippi River Commission, especially for the year that describes the flood of 1903. In addition to this study of the documents of the Mississippi River, the gentlemen desiring to know what is the matter with the river and with the controllers of the river should by all means go down the Mississippi and take jobs on the mattress work; perhaps pull an oar for the river surveyors--I think they use motor-boats now, but when I was down there, they rowed-- and listen to the things the men on the jobs say. A few hours in a levee camp, sitting around the commissary stove along toward the end of a levee contract, will add interesting supplementary evidence to that found in the documents. Sometimes it gets into the documents, for none writhes more, under the political phase of this matter, than the honest officers. It was on the Mississippi job, for example, that the army men waited for the hour when the nation would call them to the honest effort at Panama. Consider their feelings when they sent dredges to Wolf River, at Memphis, year after year, to take out sawdust. The men who conquered Panama could conquer the Mississippi River; let no one doubt that. But just as long as the men on the Mississippi River job are held to the whims of congressmen and senators and levee boards, and even to the demands of cotton planters who own three miles fronting on a Government levee--just so long the Mississippi River shall go on its course, filling up its bed with 200,000,000 cubic yards of material, while the Government keeps on piling up its little levee system on both banks, doing very little permanent or adequate work. On page 46, "Survey of the Mississippi River" (1909), is a little table. It tells how much the annual cave is in various river bends. The average from Cairo to Donaldsonville is 9% acres to a depth of 66 feet, or 1,003,579 cubic yards. The distance by river is 885 miles. That is, 850,000,000 cubic yards of material washed down stream. During nine months of the year, floating sediment to the quantity of 187,000,000 cubic yards came down the Missouri into this lower river. Besides this floating sediment, the river of mud, sand and gravel at the bottom of the water must be reckoned with. In all, the Missouri is dumping fully 400,000,000 cubic yards into the Mississippi, where the Government is heaping up three of four million cubic yards of dirt a year, to counteract the effect of this channel deposit. Why not bring the men who dug the Panama Canal back to the Mississippi and give them the opportunity to assail their ancient enemy, unimpeded by the contemptible politics that has restrained the impatient men who know what to do, and would do it to the everlasting advantage of the country? When those men were beyond the reach of the picayune influences, and were left at least sufficiently alone in their work they conjugated the verb To Do. They are the men who know; they don't own cotton plantations, nor boom swamp lands, nor sit on railroad directorates, nor speculate in sugar and rice--they see their duty; and the one thing in all the world that they would rather do is their duty. All that stops them is the--we all know, and the more shame to us since we do know. Give them a chance! Little Falls, N. Y. RAYMOND S. SPEAKS.
