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GORRESPONDENGE. S~We do not hold ourselves responsible in any way for the views or opinions expressed by our correspondents. It is our desire that all cides of any question affecting the interests or welfare of the lake ma- rine should be fairly represented in TE Maning Recorp. ee WHERE ARE WE AT? 10 the Editor of The Marine Record: It seems from the last issue of. your:journal—June 2¢ —that our friend G. W. L. is becoming hypercritical. - He objects now to calling those courses that pass through cardinal points rhuimb-lines, and quotes some authorities to support the idea. But::he and the authorities whom he quotes should know that this is an unsurmountable, untenable and unnecessary distinction. Not one of the 14 defini- tions quoted in his letter to THE MARINE RECORD for May 28 recognizes any such distinction, but, on the contrary, some of them distinctly teach the contrary. Thus, ‘rhumd.” ‘Any straight line on the chart (Mercator projection) represents a rhumb-lise,’’ etc.— U.S. C. and Geodetic Survey Report.. This authority _should be sufficient on this point. Our friend should remember that all regular curves— and the rhumb-line is one of them—have what are known as ‘‘stagular” points, z.¢., points in which the curve has some features or characteristics that it has -motin other positions. To illustrate: Say that we, in north latitude, have a ship’s track running due east a _ given distance. This track, on the earth is the arc of a true circle. Now conceive this track, which is.con- caye to the left, to be swung bodily to the left about its western extremity; the curvature will begin immediate- ly to be diminished, and more rapidly in the lower than in the higher latitude. This reduction in the curvature will be continued till the meridian is reached, when that element that measured the curvature vanishes, and the rhumb or track of ship becomes.a right line. The swing of the rhumb-line being continued, that element of the curve:that ‘‘vanished”’ on the east side of ‘the meridian reappears on the west’ side, but with a contrary sign—z. ¢., the rhumb has become concave to the right—~. ¢., the direction of flexure is changed. So when the curve passes the prime vertical, or east- west point, the flexure of the curve changes direction again, the convex side always being towards the prime ‘vertical; and the concave side always towards the mer- idian, yet in all these different positions the curve is represented bya right line onthe Mercator chart, and is always indicative of the correct course of ship. So that notwithstanding the opinion of our friend and the four eminent authorities quoted to the contrary, we ‘must still regard any right line on the Mercator chart as a ‘‘rhumb-line.’’ Mr. G. W. Ly. is very anxious that I should know that there is but one kind of rhumb-line, and brings upa formidable array of authority in support of that idea. It is quite certain that most of the authorities quoted recognize but one rhumb-line, and in the sense as un- derstood by them, and as correctly defined by the American Practical Navigator (Bowditch), there is but one; but it does not fellow that therefore there is no other line having precisely the same conditions with the several lines which it crosses, as does the orthodox rhumb with the seyeral lines which it crosses. This orthodox rhumb, or geographic rhumb, crosses all the geographic meridians, within its limit, on the same angle for any given course. The ship’s track (magnetic rhumb) crosses all the magnetic meridians within its limit, on the same angle, for any given course. And what is more, the angle of the rhumb for any course, is identical in value, on any geographic meridian, with the angle of the ship’s track on the corresponding magnetic meridian. In other words, the angle of the rhumb for any course, is precisely equal to the angle of the ship’s track (magnetic rhumb) for the same course. Here are two lines, separate and distinct, one a right line, the other acurve (on the Mercator chart) that, when referred to their respective meridians, answer precisely the same conditions»or requirements. Now, ifI may not call the ship’s track a magnetic _ rhumb, will our friend G. W.L. tell us what we may callit? Iam not particular about the name, if it will recognize the difference between the rhumbz-line, as commonly understood, and the ship’s track. THE MARINE RECORD. This difference is what I want brought out where it can be seen and measured, and be made a visible, tang- ible quantity. A little note of further, or supplemented instruction on our excellent charts, would remove this long-endured stumbling block from further annoying our shipmasters. H. C. PEARSONS, Ferrysburg, Mich., June 29. ——— Pare — oe BUILDING OF RACING SHELLS. (CONTINUED FROM PAGE 7.) Sire eg ane POR a eerste ier eee eT mee nT of greater importance. An expert sculler will have his shell built to suit himself and rigged to fit his arms, legs, etc.; why then should we expect amateurs to be without individuality and force them to accommodate themselves to the riggings, instead of vice versa? Looking more critically into reasons and causes, we find the deplorable condition that a tacit combination seems to exist among those in power to kill off all new departures as long as they do not emanate from them- selves. The college oarsmen do not stay long enough to even learn to understand the principles involved in rowing, and while there are a great many able men among them, they have not time to even suspect the importance of the mechanical and other great truths which seem paradoxical to the casual observer. The inventor is, however, not always to be found among the college-bred coaches, and asa result, we find at the present time the riggings used by our leading college crews behind the times. It would be requiring consid- erable space to go into the details of the state of affairs at the different universities, but from all indications it is safe to say that there appears to be a glimmer of radical change on the horizon. The literature on matters pertaining to. rowing is ac- tually the worst and most meager imaginable, consider- ing the universality of the practice. What has appeared in late years is hardly worth mentioning, yet it is a rec- ognized fact that asan exercise, the art of rowing is given first rank. But in order to be an exercise and to be beneficial, not enough attention can be given to the details of riggings in order to insure normal develop- ment of muscles, and not, on the contrary, produce spinal troubles and other ailments. With the ordinary sweep, for instance, and a man always pulling on the same side of the boat, an abnormal, one-sided develop- ment cannot be avoided, and the physicians will hail the new swivel oar invented by M. F.. Davis, allowing the equal use of both arms, with delight. No man has brought the racing shell as now used to such scientific perfection as M. F. Davis, who for nearly thirty yearsas amateur, professional oarsman, builder, coach, and especially inventor, has been a succession of surprises to the aquatic profession. It was he who first used a sliding seat, the swivel rowlock. It was he who first taught Donaghue to make a racing oar, advertised by this man for years as Davis’ patent; he who invented the present rowing shoe, the hollow oars, the metal but- ton, the rubber rowing handle, the water-proof cedar planking, the anti-crab attachmentifor oars, the three- rod outrigger, etc., and to-day he appears with another surprise of the greatest importance, the ‘‘Swivel Oar,” which will undoubtedly revolutionize accepted theories and methods. The writer was favored with a glimpse of the new things still in store by a representative of the Detroit Boat Works, who have taken hold of all of Mr. Davis’ patent devices and are now supplying the demand for them on a large scale. Their doing so has freed Mr. Davis sufficiently that he may now devote his time to perfecting a large number of inventions still in the ex- perimental stage. ‘The writer inspected at the Detroit Boat Works a num- ber of shells partly under construction, partly ready for shipment. Singles which weighed complete with all rigging less than 25 pounds, doubles of less than 42 pounds, fours less than 90 pounds, and an eight of less than 200 pounds, while they are prepared to reduce single to 21 pounds, pairs to 40 pounds, fours to 88 and eights to 195 pounds. In comparing these weights with those of other makers, it must be emphasized that they include outriggers and locks, generally not counted. As a single is over:'30 feet, and a four 46 feet in length, these light constructions could only be obtained by the most careful selection and combination of parts. All previous attempts by others to build light shells have invariably resulted in weak boats, while the Detroit shells, even the long eights (68 feet in length) can be carried at the two extreme ends without risk” or show- ing undue strain. The Wyandotte crew pronounce their new Detroit shell of 95 pounds weight, incompara- tively stiffer than the 160: pounds shell they rowed last — year. This result as mentioned is obtained by careful studying every minute part as to load and var : strains. The planking is composite, in singles less than one- thirteenth of an inch in thickness, combining the ad- vantages of the natural elasticity of the cedar with the toughness of the paper, without the fault of the former being early split, or of the latter of being in time satur- ated with water and becoming loggish and soft. No pro- fessional or expert will use paper in matched races, ~ The gunwales and keelsons in these boats are in one length, and the internal bracings consist of a system of diagonals, made of hollow tubing of exceedingly light gauges, increasing in diameter toward the cockpit. There they connect with metal brackets and outriggers in such manner that ‘strains from one side equalize those from the opposite. In the old and still. commonly used types of shells, the sides of the cockpit are utilized as indispensable members of construction and have to sup- port the outriggers solely, which requires them to be made at least from % to 5 of an inch in thickness, while in Davis’ shells, the only function of these sides is to keep out the water, and they are conseq uently re- duced to less than % of an inchin thickness. In these shells the parts are mostly interchangeable, all metal parts are metal to metal, and outriggers can be raised or lowered at once without the application of washers. The footboards are adjustable, the steering gear is self-locking, the seats have curved tracks and are anti- frictional, and have improved flexible tops. The oar- locks are adjustable to any desired angle of anchorage of blade, and their pivots have adjustable bearings. They have an attachment against crabbing and easily replaced leather buffers on which the metal buttons on the oars play without friction, lost motion or noise. The model of the shells is one of least resistance, sec- tions being of semi-concentric shape, while Mr. Davis has always advocated length as the prime element for speed. - We now return to the new swivel oar which the writer had occasion to inspect. The accompanying cut shows this oar in action, It enables the rower to use both arms equally, to maintain an approximate, uniform motion fore and aft in rowing, to gain from extreme forward to extreme after position with same length of oar outboard as ordinarily used (32 inches), to lift oars higher out of the water in rough seas, to bring the oar- lock:closer to the water, as the gooseneck will pass over the knee where an ordinary oar would strike, etc., while no advantage of the old oar is lost. Any of these points would be of sufficient importance to invite attention, and while expert oarsmen have only one yoice in its favor, and are vieing in speculating on its merit, some of our college coaches have deemed it wise to ignore its arrival, since it did not come from England, ‘you know.”’ In this connection it. is interesting to note a report from Henley, saying that coach Bob Cook spent two hours to teach his crew from Yale the Cook catch, which means the proper entering of blade after recovery. A simple device invented by Davis, and attached to the oar, insures the proper catch automatically, surer than any expert could learn to perform it with years of prac- tice, yet two valuable hours on the eve of an important international race are wasted to learn what any novice could perform unconsciously with the Davis device without tuition. The remarkable success which M. F. Davis has had in this line is due to his inventive turn of mind, his pugnacious nature, his ability as an expert oarsman to personally try and manufacture all parts entering into the construction, his conservative way to never over- estimate his own merits and inventions, and to never try to put them on the market until thoroughly tried. His inventions have been most shamefully appropriated by infringers, and he is to be congratulated to have found with the Detroit Boat Works, who have taken hold of the manufacturing of his inventions, a concern that will guard his interest. HucuH M. McCorMack.