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THE MARINE RECORD. Correspondence. ‘B@- We do not hold ourselves responsible in any way for the views or opinions oxpressed by our correspondents. It is our desire that all sides ‘of any question affecting the interests or welfare of the lake marine should be fairly represented in THE MARINE RECORD. ot hona NN ll dtc ata IN LINE WITH “BEGINNER.” CLEVELAND, O., February 10, 1892. To the Editor of The Marine Record. 7 Learning that my former communication was received too Jate for insertion in your issue of the 4th, I now contribute the Azimuth worked out nearly according to “Begioner’s’’ in- structions. Alt, @L.L. 4° 50/ 007 Decl. 7° 09S Ref. & Par. — 10 01 90 Cor. Alt. 4 39 59 P.D.97 09 ©Semi-dia, + 16 04 Alt. 4 56 Sec. = 0.001612 —__—_——. Lat. 47 00 Sec. = 0.166352 True Alt. 4 56 08 a ———_ Sum 149 06 74 33 Co. Sine 9.425530 Rmdr, 22 36 = Co. Sine 9.965301 19.558795 + 2 — 9.779397 — Sine 4 Az. = 36° 59’. The true ‘Azimuth is therefore 8. 73° 58’ W., and by applying the kuown variation the error of the compass is found for that course on which the vessel was heading at the time of taking the bearing. ‘Beginner’ unless he has misquoted himself says to reckon this Az. from the N., Norie says if Lat. is N. reckon from $. and vice versa, SrupEyt. NAUTICAL MILE VS. MINUTE. Mitwavker, Wis., February 8, 1892. 14o the Editor of The Marine Record. In your issue of January 14th, our well known wriler on nautical matters, H. ©. Pearson, wishes to convince us as to the unfitness of a nautical mile asa standard length measure or unit. But, as Mr. Pearson makes himself! liable to a few contradictious, he will probably excuse our determination not to accept his decision in the matter. After explaining that the length of a nautical mile has been decided to be 6080 feet, he shortly afterwards expresses him- self thus: ‘‘The nautical mile is not a concrete quantity like other units, but merely a ratio, a certain part of a whole, with- out regard to size.” But how is this Mr. Pearson? We just noticed you to say, that a nautical mile contained, consisted, and expressed the certain quantity or length of 6080 feet, and now you claim those 6080 feet to be “‘not a concrete quantity.”” Is not a foot a certain length or quantity ? If it is, is not also 6080 feet or a nautical mile something concrete and unchange- able? Ifaautical mile was identical to and expressed the same meaning as a minute, why decide it to contain 6080 feet ? Why use the expression mile or more commonly ‘‘knot,”’ in- stead of retaining the original word minute? Will Mr. Pear- son kindly explain this to us unfortunate enough to stumble in the darkness. In our opinion a nautical mile is a concrete quantity, a cer— tain length containing 6080 feet and fully adaptable to any practical purpose as a unit or length measure. And a minute is, to use Mr, Pearson’s words, but merely a ratio, a certain part of a whole, without regard to size, But, furthermore, a minute is something abstract, the size of which as a length unit can be imugined only on the curve of the angle it represents, sae radius is known, Because, with an unknown length as radius, a minute might as well express a length of one foot as that of 6080 feet. i But for instance, where a radius is known as that of the glob I e being 20,925,000 feet, those being the closest round feueee: the minute of the curve detained with that length as rodius expresses a length of 6087 feet. We would therefore be justi- fied in modifying a certain phrase of Mr. Pearsons article and read it thus: There are just as many minutes in the equator of the school globe, as in the equator of the terrestrial globe, though not quite so many miles, neither nautical or statute miles, as each of them express a certain length measure and as such are unchangeable. We could also express our dis- tance sailed in minutes, by always using the radius of the earih as thereby we would always be sailing on the curve of the same radius, and a minute in that instance, be equal to a nauti- eal mile. But otherwise, a mile and « minute, will each main- iain their distinct meaning. Avourn L, Frirrscu. “BEGINNER’S” PROBLEM SOLVED. . Toronto, February 8, 1892, To The Editor of The Marine Record. Your correspondence columns have for some time past con- tained much matter of great interest to the shipmaster who deals in nautical problems, notably, the much vexed subject “Change of variation, and variation proper.”’ : Friend Pearson appears to assume that none of the other writers can discern the difference between the two. 1 interpret their written opinions different from his. It seems like splitting hairs over a sentence that all understand alike. I have oe doubt but each correspondent would, if bound on a voyage from Buffalo to Toledo, or vice versa, take the mean variation between 5° W, at Buffalo and 0° at Toledo, and use us a cor- recting course 2}° to the right going either way. The very slight curves made by so doing would not affect the distance to any appreciable degree. When your correspondents speak of change of variation setting them to the north, they touch the very gist of the question, and show the need of knowled, @ on the subject, us it is the business of the skilled belgian to know what the change will do with his vessel certain the method of correcting it, i Fon noi ondent und: u nden' i i ner” puts two Rison hein pong a “tow to fn ara viation of the compass and apply it correctly. ?”” pene de. The reply to that cannot be given in the space your paper » how to as- and how to apply the cor~ couldafford. As recommended in my letter in your columns on Angust 30th, 1891, let the user provide himself with a good pelorus or azimuth compass, and Burwood’s azimuth tables, | go to some teacher of nautical astronomy, study quietly fora short time, and he will then be able to ascertain his compass errors accurately and readily by sun or star azimuths, the most accurate method in use among navigators. He will also be able to solve the problem put in “Beginner’s’’ second question, viz. On Lake Superior, October 11, 1891, p. m., altitude of sun’s lower limb 4° 50’, latitude 47° .01/ N., sun’s declination 7° 09/ S.; with those elements he would go to his epitome of navigation and work out the azimuth or sun’s true bearing and find it N. 105° 54” W., or he would with the same elements work out the apparent time at ship when the problem was given, and find it4h, 23 m. 20 sec. pm; with that apparent time go to Burwood’s tables and take out the azimuth, finding it there N. 105° 54’ W., precisely the same as when worked by the logarithm method. Having thus obtained the sun’s true bearing, apply the variation, in this case say 3° E, making the sun’s correct magnetic bearing N. 108° 54” W., the sun’s com- pass bearing cannot be given only by the observer as the com- pass error is not stated, and here again may I impress the fact that no ordinary placed compass upon an iron vessel can be en- tirely free from errors after the most skilled adjustment, hence, the importance of having ship swung frequently to ascertain and apply the small errors found thereby to the courses shaped, I assume by the form of the questions put, that “Beginner” is an expert at nautical astronomy, and thus look in the future for his confirmation of these suggestions of mine. W. H. GoopreLiow. MERCATOR VS. CONICAL PROJECTION, Dututu, Minn., February 9, 1892. To the Editor of The Marine Record. In your issue of the 14th ult. we are gravely informed by “Spectator’’ that courses as found by our lake charts, always tend to take a vessel to the north of her intended course, and then he enquires if that fact has ever occurred to us, as if we were in some way responsible for it, or that we were guilty of some serious neglect in not treating it in connection with variation, to which he refers. We would respectfully report to ‘‘Spectator” that no such fact has ever occurred to us, nor do we expect that any such fact ever will occur to us, for the reason that there is no such fact to occur to anybody. But it did occur to us a good many years ago, that there is a property of conic projections by which & vessel may be dey- iated to the north of her proper course, though not necessarily so, nor so much as ‘‘Spectator’’ would have us believe. In the case mentioned, Buffalo-Tuledo if he will multiply the sine of the mean latitude of the two places, by their differ- ence of longitude, he will have the inclination of the meridian of those two places, thus: Mean Iatitude, say 42°, sine 669. Diff. longitude 33°. Product=3} x 669—2}°, and not 3° as we are told. Then as only half of this inclination can affect the bearing at each end of the route, we have only 14° as a possible error instead of 3° as certain error. Again, it is not the distance sailed, but the amount of longi- tude embraced by a single course, that determines the incli- nation of the meridians, embracing that course. Probably the one course covering the greatest amonnt or difference of longitude, is that of Long Poiut—Point Pelee, embracing 23°, then, .669 x 2}°—1.°67, the half of which, or .82 of 1°, or about } of } of a point, is the possible error of the course, anamount far within the ordinary non—precision of steering ship, and therefore absolutely inappreciable. And, even this infinitesimal tendency to error may be avoided by applying the protractor to the middle, or near the middle meridian when taking up course. To avoid this trouble, which he calls a “great inconvenience in practice,’ he would throw our lake charts away, and adopt Mercator’s chart. Now it should be known that while for large areas like that of a continent, or the half, or even the whole surface of the earth the Mercator projection is the best; the conic projection is the best for smaller areas, as for a combined area of a few of our States. In Mercator’s projection, distance, that element so important to navigators, does not yield to scale and dividers without num- erical work, which would require a kind of training to which our people have never been accustomed, To introduce such an embarassment so long as our conical projections yield dis- tance at once, and correctly to scale and dividers, and course to absolute accuracy, as we have seen, would seem to he a very idle and foolish thing todo. Yet our learned ‘‘Spectator’’ tells us that ‘‘to come up to modern times, lake charts have to be on Mereator’s projection,’’ but the reason for such necessity he does not give us—perhaps he had not the time. In your issue of January 21st., in speaking of my reply to “Surveyor,” he undertakes to quote my figures for the value of the minute of a degree in different places, but makes three consecutive mistakes, giving my equatorial minute as my mer- idional minute. And my mean minute of the meridian, up to 80° of latitude, as my value of one minute of the meridian at 80° of latitude—a very different thing, Again, in comparing my figures with those of Prof. Young, he gives my equatorial minute as a meridional minute, My figures for the value of one minute in different places, are rigorously correct, and correctly given on page 6 of Tue Marine Recorp issue of January 14, and when the figures for the same locality, are compared with those of Professor Young, they agree precisely—the seeming discrepancy re- sulting from the blundering of our learn whose hand we have seen before. Again he tells us that the absurdity of using the statut in nauticul computations, appears from the fact that no ¢ putations can be made with reference to place, in which miles have not to be reduced to nautical miles at the ae or at the end of the reckoning.”’ We are sorry to be obliged to dispute the statements of distinguished ‘‘Spectator’’ so often. But to show that above statement is absolutely false—for whut reason we can: tell—we give illustration. = All, or nearly all works on navigation and nautical survey: and geodesy, give tables of the value of one degree of longi. tude, at every degree of latitude—both in statute miles and in nautical miles. Anda well known method of reducing di ture given in either of these units, is identical for both, t To reduce departure given in statute miles, to difference longitude. Rule, divide the departure by the number of statute mi in a degree at tae mean latitude, and— a Reduce departure given in nautical miles to difference of longitude. “4 Rule, divide the departure by the number of nautical miles in a degree, at the mean latitude. Here we have reduced distance given in statute miles, toone of the co-ordinates of place, without first or last reducing it to nautical miles. What “Spectator” can mean by making such a statement we cannot understand. We cannot see how itcan be the result of ignorance, for the problem is within the easy reach of any 14 year old school boy. : Once more—He pooh-poobs the idea that the records of the astronomical work that has been done by the government, and given to us in the United States List of Lights for the lakes, may be utilized as an aid to navigation on the lakes, in place of nautical astronomy, now that we have standard time estab- lished. Hear him, ‘‘A dozen chronometers showing standard time avail nothing in navigation, if ship time is not known, which must be found by astronomical obseryation.”’” Andin a previous remark he implies that ‘every pebble stone on the Great Lakes,’’? may be as well referred to as the lights for information. No doubt “Spectator” could do as well referr- ing to the ‘pebble stones” as to the lighthouses, for we have seen such men. But our maritime people, not being so profoundly learned that they can deduce the desired aid from the ‘‘pebble stones,” I offer the following plan of deducing oneaid, say thatof time at ship—from knowing the place of a light. A good waich adjusted to standard time, on the lakes is a perfect anulogue of the chronometer at sea, each gives the time of a known meridian. The longitude of any light is given in the List of Lights. The difference of longitude between the standard meridian and that of the light, or ship, which we will call the local mer idian, when reduced to time, at 4 minutes per degree, gives us the difference of time between the cau meridian and the local meridian, whence mean time becomes known at ship. Again, the Nautical Almanac gives us the difference of mean time and apparent time for the date, under the heading “Equation of Time,” which applied to mean time at ship, gives us the apparent time at ship. Thus, without the instruments and field work of nautical ai- tronomy, we haye deduced one most important aid to navi- gation. ‘The uses and importance of this element are precisely the same on the lakes as at sea; and other elements may be de- duced with the same facility. Then why not utilize the infor~ mation given in the list of lights, thereby saving to our mari- time people the expense of nautical instruments, and a long course in nautical astronomy, with its requisite mathematical training, also a long course. The “place” of ship on the lakes is found by dead reckoning, precisely as at sea, and with the same certainty, for the method in itself, is rigorously correct, and for runs of one or two days, as on the lakes, is all that can be desired, At sea, after # short time, external causes, as unknown or imperfectly known currents, imperfectly measured leeway or drifi, conspire vitiate the results of dead reckoning so as to require correction by astronomical work. What our friend ‘Spectator’ can mean by discouraging the | idea of utilizing work already done, and which can be bad for the asking, considering the apparent intelligence he shows in some things, we can hardly impute it to ignorance, then pray — tell us what is it? , There are many other beauties in the two communications above referred to, which to develop according to their merits, would require another chapter, suck as is here given, but this must suffice. * “ ‘There is nothing that gives me so much pleasure as to dis- cuss such questions as I can discuss, with those who are look- ing for light. But when I am brought into contact with arro- — gant dogmatism, I confess that my religious training has not — been so perfect as to enable me at wll times to hide my “con- tempt of court,” with as much grace as could be desired. H. ©, PEARSONS. ade WORLD’S FAIR. General Manager David Carter of the D, & C. Navigation Co., in reply to a letter from the traffic manager of the World’: Columbian Exposition, has just sent the following letter: E Derrorr, Micu., February 4, 1892, E, E. Jaycox, Traffic M’g’r World’s Columbian Exposition, Chicago, Ills. < Dear Sir:—Yours of the 2nd addressed to James MeMi president of this company, who is at present in the U States Senate at Washington, D, C., has been referred to 1 In reply would say that it will be impossible for this comp to send any of its steamers to Chicago in 1893, for the tr portation of passengers to and from the Exposition. steamers are all engaged on important routes, which wi take care of, regardless’ of other tempting offers, and ‘this lieve, that we have steamers that could do the whole business. 1 oh ectiully yours, Me Be Very res 4 . CARTER, General A recEN? Englis’ invention is a serew propeller, the blades can be adjusted for maneuyring or can be ed for running under sail, - hi a