The following text may have been generated by Optical Character Recognition, with varying degrees of accuracy. Reader beware!

one and the same thing under any and all conditions. Little wonder then, that these terms prove such stumbling blocks to the uninformed, and confuse even many thinking men. There is a wide difference in them and each has a distinct meaning of its own, as has already been shown (and to be shown) are properly interchangeable and therefore indefinite. USE CORRECT MAGNETIC ALTOGETHER, Note.--It will be well for the stu- dent to use correct magnetic course or bearing altogether instead of magnetic course or bearing, and thereby avoid possible confusion, for in the regular run of correcting courses it will be correct magnetic, and as we have seen it cannot be anything else only under certain conditions, which conditions are hardly, if ever, used. SOME BOOKS MAKE NO DISTINCTION. Some books use magnetic course or bearing altogether and never' even mention correct magnetic course or bearing. They seem to think that it is an advantage to drop the word "correct.".* As we have learned a magnetic - course or bearing is the natural direction of the compass needle when influenced only by the earth's magnetism, and a correct mag- netic course is a true course corrected for variation. THE EXPRESSION ORIGINATED WITH TOWSON. This very convenient term of "Cor- rect Magnetic" (in place of '"Mag- netic") was 2introduced by the late Mr. J. T. Towson, an Paglishman of acknowledged high authority; and as Captain Lecky says, being concise, and not admitting of ambiguity; it has met with ready acceptance by a large majority of thinking men, but the min- ority, and some of the _ loose-jointed, slipshod members of the profession, think the first word unnecessary, and that it would be an advantage to drop it. With this we do not agree. Some- thing therefore is wanted to prevent confusion which must necessarily ex- ist in its use, hence the simple prefix "correct" serves the purpose admira- bly, and therefore renders clashing im- possible. When "magnetic course' is used in place of "correct magnetic" the expression is illogical. MUST GET A BETTER REASON. Because the mariner's compass is a magnetic instrument it does. not fol- low that the course steered 6r the directions shown by it are "magnetic" any more than "correct magnetic," 'true' or "compass.' Each of these courses have a distinct meaning of their own, and they are widely differ- ent from one another, notwithstanding the fact that they all originate and are used in connection with the one "TAE MARINE REVIEW instrument. To the uninformed. there would seem to be no difference in the expressions "magnetic" course and "compass" course, since both are shown on the one instrument. Of course it must be admitted that since the mariner's compass is a magnetic instrument, that by its aid a magnetic course of some kind could be steered whether correct or incorrect. ANOTHER ILLUSTRATION. OF IT. Again, supposing the case where the true course is south and the Var. is %-point Wly.; then magnetic south is %4-point to the left of true south, but the point of the compass coincid- ing with true south is '%4-point to the right of magnetic south, or S%ZW which is the correct magnetic point for south (see diagram) therefore to steer true south you would have to steer SYW. If you steered south by compass (the magnetic course) you ! would be steering SY%E true instead of south as your compass shows. By allowing the variation to the true course gives thé very same thing, thus 14-point to the right of south gives S%W\, the correct magnetic -course. But to. find. the true « course. alter steering south by compass allow the 4-point of Wly.:Var. to the left of south, to get the true. course run, would be S%E. 'Thus, in the above case. the true. course is south; the magnetic course is S%E and the correct. magnetic course is S%W Again, we are brought to a realization of the distinction in the expressions "Magnetic" and "Correct Magnetic." As we said before, in order to avoid confu- 'sion it will be well to use correct mag- netic altogether instead of magnetic. In fact there can only be a few cases where the magnetic course or bearing is con- sidered. SOME ILLUSTRATIVE EXAMPLES. To resume with the conversion of cor- rect magnetic courses to true courses: If the C. M. C, is W by N, Var. 1 pt. Wly., what is the true course? Ans. West, because Wly. Var. is applied to the left when converting a C. M. C. toa T. C.; therefore 1 pt. to the left of W by N is West. Supposing the C. M. C. to be N by W with 1 pt. of Ely. Var., what is the cor- responding true course? Ans. North. We will now take some of the exam- ples that we have been working and turn them from correct magnetic to true. The C.M. C. is N by EXE, Var. 3%4 points Wly., what is the true course? C.M.CN by EZ E=1% pts. R of N Var. Wly. 2 True Course 134 So of [=N by WY%W Here the Var. exceeds the course, so 37 the course is taken from the variation and R changed to L.; 3% is the same as 2 5-4, so that 134 from 2 5-4 is 1%. The CM. Cis NNE: Var. 2 pts. Wly., what is the true course? C. MrC. NNE=2 pts. R of N Vat Wily @ oe 8 Ee True Course o= North. The C. NEC, is WSW, Var. 2 pts. Ely., what is the true course? Co M: C.UWSW=6 R of S Var. Ely. 2R True Course 8 R of S=West. . The C. M. C. is S 56° W, Var. 6° Ely., true course. C. M.C=s6° R ar S, or SW by W, a Var, Bly oR -Teept. co: T. C. 62°-R of S, or SW by WY4W the (2M is N33" W, Var. a Wly., what is the true course? C. M. C==23° L.of N Var. Wily. 47 3b T. C. 47° L of N, or NNWHW, nearly, ; The correct magnetic course from Chicago to Pt. Betsey is N by E%4E, the mean Var. (what mean Var. is is ex- plained further on) is approximately 4 pt. Ely., what is the true course between these points? Ans. N by EYE The lighthouses on the NWly. and SEly. ends of the. Chicago breakwater range NW by WY%4W (that is the way 'your compass ought to read when on with this ropes -with no deviation) the Var. being 3° Ely., what is:the true bear- ing of this range? Ans. NW by WYZW _ TURN THE YAR. INTO POINTS. In practical work it is found more convenient to turn the variation, which is 'always expressed, in degrees, into its equivalent in points, but where greater accuracy is sometimes required -- the course should also be expressed in de- grees and fractions of a degree. Thus, the above example would be as follows: NW by W%4W=6r° 53' L of N Mar, Ely. ar R True bearing 58: 53 L of.N, or NW ' [by WYW 'NoteWhen there is no variation the true course is also the correct magnetic course and vice versa. ANOTHER METHOD OF CORRECTING COURSES. If the student has carefully gone through the preceding examples, he will have noticed that easterly variation in its application from true to correct mag- netic courses decreases them in the NE and SW quadrants of the compass, and increases them in the NW and SE quad- rants. Westerly variation increases 'the. courses in the NE and SW quadrants,