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36 THe Marine RevIEw ms WHAT EVERY MASTER SHOULD KNOW. ' The Application of the Variation and Deviation to the True Course--How to- Separate the Var. and Dev. From the Compass Bearing, Etc. BY CLARENCE E. LONG. The Marine Review has no sympathy with mechanical processes--those operations requiring no thought--which are simply committed to memory, any more than it has with rules and formulas learned Poll-parrot fashion; and to navigate a ship by such method, is indeed, to tempt Providence. The navigator, to be a navigator, should have the principle of each problem which engages his at- tention, thoroughly learned; so that, relying upon the ac- curacy of his reasoning rather than on the distinctness of his memory, he may be able to solve it whenever called upon. The navigator, of all men, should cultivate his reasoning powers to the fullest extent, for the safety of life and prop- erty depends upon the soundness of his judgment at crit- ical times. Possessing the requisite menial sclniey and the power . of selecting the most advantageous means out of the many at his disposal, is what constitutes the real test of 4 man's ability as a navigator and shows that his knowl- edge is not superficial, but based upon strictly sound pzin- ciples, which cannot mislead. The navigator who intends to reach the "high ratline' of his profession must work hard for it, and his course must be, "The best that I can do is the poorest that I will do." No man need despair even though not specially gifted, either with intellect or education, if otherwise made of the right stuff--'grit." The race is not always to the swift, as exemplified in the fable of the hare and the tortoise. It is simply astonishing what dogged perseverance will accomplish, to which any self-taught man can readily attest. "Rules of Thumb," when founded upon correct reason- ing, are invaluable; but, on the contrary, "Rules of Thumb" not founded upon correct reasoning are a posi- tive bane to the practical man, for whose benefit they are generally intended. The navigation on the great lakes and sea cae with but a few exceptions, is performed by rules of thumb based upon incorrect reasoning. 'This navigation is too much on the mechanical-process-order, or navigation of the two-foot-rule kind. These navigators do certain things, but they are entirely ignorant of the principles in- volved; or in other words, they are unacquainted with the "whys" and "wherefores" of the methods they practice. This is noticeable in more ways than one. The ma- jority of lake captains pay no attention, whatever, to the variation of the compass existing between the place started from and the place, or turning-point sailed for; that is, they do not make the true or proper allowance for it in shaping the course to be steered. True, they allow for it in a way, but it is not done intelligently because they lack the knowledge of its governing laws and principles. In other words, they are ignorant of the first correction of the compass. In shaping a course between certain places or points on the lakes the master is guided mostly, if not wholly, by the course or courses steered over the same ground some previous time. Of course, in this way it is possible. for them to make good courses. Others again, compare pier and river ranges, which happen to coincide, or nearly so, with certain lake courses, and in this manner courses are made, but no attention is paid either to the variation or to the deviation of the compass, They may not make a good course of it the first time, but in correcting the trial course steered for the second time by porting or starboarding the proper amount to this trial course, good "hits" are made; and in this way Var. and Dev. do not enter into the problem so far as the master is concerned. But, nevertheless, it plays its part, for what is the result when it is desired to steer a course to some place outside of the regular routes of the lakes, with no ranges or other marks by which to guide the course? The master then notes a course that he has al- ready steered which coincides with, or is nearest to the one on the chart he wishes to follow. If the course he has picked out does not coincide with the one on the chart, but is near to it, say half a point, it is altered ac- cordingly so as to allow for the difference in the angle made by the two courses. When the course is run and the vessel fetches wrong the blame is not laid to its proper cause because it is not known. In miost instances, it is laid to leeway or current, Var. or Dev. having, it is sup- posed, nothing to do with it whatever. Now, it is just as likely to happen that the variation existing for the first course found is of an opposite name to the variation existing for the second course, notwith- standing that the second course is determined from the first course. That is to say, if the variation in one case was easterly it would be vey in the other, or vice versa, To illustrate this we will take a practical example: From Sault canal on ranges (over stern) the true bearing or direction is W by S 4% S (WSW 3%. W). Var. for this position about 21%4° Wly. (equals %-pt. nearly); making the correct magnetic bearing of the range W by S (Var. Wly. allow to the right of the true course or bearing, to get correct magnetic course or bearing); that is to say, were the compass absolutely correct (free from Dev.) when the vessel headed in this direction (ranges directly over stern) and no other magnetic attraction other than the earth's, which gives the compass needle its directive - force or pointing power, the compass would read W by S. From a position 5 miles north of Eagle Harbor to Devil's island the true course is W by S 4% S (WSW) % W), same as Sault canal ranges; Var. at Eagle Harbor about 214° Ely. and at Devil's island about 6° Ely., the mean of which is 4%4°, equal to 3£-pt., making the correct magnetic course W by S 5% S (WSW % W)--Ely. Var. allow to the left of true course or bearing, to get correct magnetic course or bearing. Here we have the true dir- ections precisely the same, but when the Var. is' applied to make correct magnetic directions (that is, the applica- tion of the Vaf. to the true course) of them they differ by Sg-point, or .7°; nevertheless, in either case, the vessel is heading true W by S 14.5. .* The uninformed master entertains the idea that be- cause this range and course are one and the same true directions that whatever the compass reads when his boat is On with the range, represents the course to be steered . by that particular compass from Eagle harbor to Devil's island. These true directions are nevertheless the same, but it is the change in the name of the Var. that accounts for it, the Dev. taking no part in the problem, because it remains the same for that heading of the vessel whether in the Sault river or on Lake Superior, providing, how- ever, that the change of latitude is not too gzeat. : Where the name and change of the Var. is of the same name and amount, this practice is sufficiently accurate for all prac- tical purposes; in fact, it is used a great deal and with good results, but it will not work on the same principle all over the lakes for the reason that the Var. is not of the same amount and name. To render this the more comprehensive we will go on with the sample example: Supposing that when the vessel was on with this range the compass read W % S, instead