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6 GORRESPONDENGE. ay-We do not hold ourselves responsible in any way for the views or opinions expressed by our correspondents. It is our desire that all sides of any question affecting the interests or welfare of the lake ma- rine should be fairly represented in Tux Marine Recorp. ee HOW MANY RHUMB-LINES. To the Editor of The Marine Record: In your issue of May 28th, lam cited by our friend G. W. L., of Washington, to show by what authority, if any, besides my own, I presume to utter the “erroneous idea” that there are two rhumb-lines to be considered in the science of navigation. . As he appears to be anxious that this ‘‘error,”” which we might call a nautical heresy, should not become cur- rent among vesselmea, I hasten to answer. But I would suggest that this heresy is on the other side of the house —that the blind eye is on the other horse, as a very lit- tle investigation will show. I will show him the two rhumbs—or if it will be less offensive, or less heretical—we will say the two forms of the same rhumb, side by side, when he can see their difference, and how they are derived from the same course. To illustrate this idea, we will state a case, say on Lake Superior, from Whitefish Point Light, to the light at the mouth of the canal at Duluth. These two lights being on the same parallel within the fraction of a minute, we may say thecourse between them is due east and west. Then a right line between them, on our new charts, will be the geographic rhumb line required. (See diagram). From the intersections of the several meridians with this line, set off the corresponding variation from the geographic meridians, when we have the corresponding magnetic meridian—the variation for each point being taken directly from the chart. Thus, for longitude 85° W, we find the magnetic meridian }2° to the left of geo- graphic meridian. For longitude 86°, it is %° to the right—2%° to the right at longitude 87° and 8° to the right at 92° W. In shaping course, we are instructed by the chart to apply the variation to the geographic course thereby finding the equivalent magnetic course—and thus rec- ognizing that the course or track of shipis referred to the magnetic meridian is shaped from them, though it was derived from the geographic meridians—a very different thing. Now, as the relation of these magnetic meridians to the seographic rhumb is very different from that of the geographic meridians, the rhumb produced from them by any course, will be very different from the geo graphic rhumb. Here we have in a nutshell the reason of the two rhumbs from the same course, and if our friend can dis- prove the construction, he can disprove the deduction of Euclid’s logic. As the variation at the point of depart- ure is practically nothing, the reading of the magnetic card will also be due west, thus crossing the magnetic meridians at right angles, the convergency of these meridians giving a curvature to the ship’s track or rhumb. Here we have the right line A. B., as the geograghic Ar “Hr? rhumb, leading ship directly to Duluth light,—while the curved line A. C. is the magnetic rhumb, leading ship to'a point some 24 miles tc the north of Duluth, on the mounta.n. (This problem is, of course, hypothetical, ignoring the rocks on Keweenaw Point.) The difference between these two rhumbs, has been a stumbling block for our shipmasters ever since our his- tory on the lakes began. They have never been able to THE MARINE RECORD. see, nor do they know to this day, why, when their com- passes are correct, their courses correct and correctly steered, they cannot make their objective point without. so mtich uncertainty in their landfall. This difference. at sea, where the change of faagoedie variation is much less and where the searoom is greater, is seldom so great as to cause inconvenience, or to at- tract attention; but on the lakes it is of vital importance —a matter of serious moment, in dark weather, causing anxiety, dread and distrust of the compass, and not in- frequently serious disaster—all from the more rapid change of the variation. It was with the view of eliciting discussion of the sub- ject, for the purpose of drawing out some plan of reduc- ing the difference between these rhumbs soas to make the ship’s track correspond more nearly with the theo- retic rhumb-line, that I presented the subject. With regard to the authorities presented by our friend. to show that there is but one kind of rhumb-line, I wish to say that he has failed in a signal manner. His first authority, (Johnson’s cyclopedia) defines both of my rhumb-lines fully, accurately and concisely—could not have doneit better myself. Whether the author wrote from a clear knowledge of the difference of the two rhumbs or merely better than he knew, or better than _ his diciples know, we cannot say, but certain it is that he has met the case fully and correctly. He says, ““Rhumd, in navigation, the track of a ship sailing on acertain course.’’ This is our magnetic rhumb pure and simple. ‘‘A rhumb cuts all the meridians at a cer- tain angle,”’—this is our geographic rhumb with the same precision. Others merely define the theoretic or geographic rhumb-line. The United States authority, knowing the difference between the ship’s track and the rhumb-line, put a sav- ing clause into their definition and give us to under- stand that ‘“‘while the ship makes the same angle with all the meridians she crosses, the track is called a rhumb-line,’’ ‘They are quite safe i in calling the ship’s track the rhumb-line on this condition, for no ship, as we have seen from the preceding discussion, ever sailed on the geographic rhuinb, when steered to a constant magnetic course. See ‘‘J. H. C. Coffin,” the MARINE RECORD of May 28, page 6. H. C. PHARSONS. EEE THE LIBRARY TABLE. “Rigs and Makeshifts of the Small Boat” is the title of an illustrated article that Dudley D. Parker con- tributes to Harper’s Round Table dated June 2d. It is of special interest, and will commend itself to yacht- men’s attention, as it contains many practical hints and suggestions on the handling of yachts. We are indebted to Secretary George F. Stone, of the Chicago Board of Trade, for a copy, handsomely bound in cloth, of the thirty-eighth annual report of the trade and commerce of Chicago. Its contents con- sist of business statistics of the fullest character, the lake figures being particularly well represented. The North American Review for June opens with a most suggestive and practical paper by Mr. Andrew Carnegie, entitled, ‘“The Shipof State Adrift,’ in which he points out the deterioratioi, since 1890, of the United States in national wealth and commercial prosperity and in plain, logical, and convincing statements, shows why such a state of things exists. The means employed to prevent danger from immigration are thoughtfully considered by Dr. Joseph H. Senner, U. S. Commissioner of Immigra- tion at Castle Garden, N. Y. President, W. J. H. Traynor, policy and power. Hon. I. Cy Parker, a U. S. district judge, writes on ‘‘How to Arrest the Increase of Homicide in America.” A dozen other able papers on live topics complete the number. “The Shipping World,’ that well-known Tondon monthly edited by Major Jones, will hereafter be issued weekly instead of monthly. It is one of the most inter- esting and handsome of Knglish marine papers, and is worthy of all success. - gee ee of the A. P. A., outlines its’ NEW INVENTIONS. “The Chase Machine Co., of Cleveland, has receive its patent (No. 561 5172). on a Compensating Mechanis for Towing. Vessels, for: which they made applicatiorz January 13, and which was illustrated and ‘descri in full in THE RECORD on May 14, The meee drawing of the towing machine 1S ‘shown in the ill Sti tion. iy To se Patent No. 561, 430 « covers ‘an [ativetor ibe the Speed of Revolution of Propellers, invented by Mathias Pfat- ischer, Philadelphia, assigner to the Electro-Dyni amo Co., of Pennsylvania. The claim is: for the combina 661.472. Speed \Indicacor a magneto eine mechanical operating eRe | between the said body and the said magneto machine, and an indicator-circuit for the said’ magneto with a suitable graduated galvanometér included therein to indicate the speed of the said shaft or rotary ‘body. Hes Henry C. Ashlin, London, Eng., has secured a patent (No. 561,472) upon a Method of Construction of Vesseeaa ES which was patented in England, May 7, 1891. His claim is for the combination, in a vessel with horizon- tally-arranged plates, arranged upon each side of the | central line of the vessel, and running longitudinally of the latter, of Z- -shaped bars or double’ angle-irons 3 having their horizontal potions secured to the . adja- cent edges of said horizontal plates, and vertical plates’ secured at their lower edges to the vertical portions bie said Z- -shaped bars. : James C, Walker of Waco, Tex., has secured a. patent, (No. 561,546) on a Life Boat, which consists of a vessel © having a series of indepently disposed water-tight com partments, and longitudinal pipes communicating with the sea, having hydraulic propulsion means for fonginy the water to the outside of the vessel. ro er The Continental Iron Works, Brooklyn, N. Y.,- have : recently supplied’ Morison Suspension Bridges to the Atlantic Works, East Boston, for steamer Ethelred; Union Iron Works, San Francisco, for steamer Queen : Hugh Ramsey, Perth Amboy, for U..S.. light house - steamer Rose; KH. Hodge & Co., Kast Boston, for steam: + er Saxon, and Howard & Roberts Boiler Works, Buf: ” falo, N. Y., for the wooden steamer William H. Grat wick. ‘They have also supplied the Harlan. & Hollings- worth Co. with a plant for-the Montaals and ° “ ges Chester.