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from Nine Mile Point to Presque isle I am not in favor of for this reason. In the vicinity of Presque isle, I think is the most dangerous place on the lakes, 'in a fog here the down bound would have to cross the bows of all up bound, both for Lake Michigan and Lake Superior, "TAE Marine REVIEW In regard to your letter of April ZU)? the question of east and west coutse © of navigating the lakes,' for my part do not think it advisable as all masters in my opinion would always make for a weather shore either bound up or down if it is blowing hard and in case of fog or show storm would naturally 29 draw in to catch 'the sound' of fog signal so as to find right location of their .- boats,°'for imstance, a Boat -tound down Lake Huron with a strong northwest wind would keep up under the west shore and would make better weather and time and it would be easier on the boat. SCIENTIFIC LAKE NAVIGATION BY CLARENCE E. LONG HOW TO GET AROUND IT, To redmove the difficulties: of large deviations as found for, the ship's head by compass instead of ship's head cor- rect magnetic, as;already explained, may ~ be done by employing the Pelorus for taking the 'bearings in the following manner: Clamp the sight vanes to the correct magnetic bear.ng of the range; unclamp the dial so as to permit it to 'move freely with the sight vanes when they are moved, that is, both should swing together; the vanes being clamped to the dial and the dial unclamped from. the rimmed disc that it works in. Then, just before the vessel is ready to cross the range keep the hair sight on the back object of the range as already ex- plained, moving it slowly and evenly to keep it there as the vessel proceeds to close and bring the two objects of the range in one. At the instant that they are in transit read the course as shown by Pelorus, also the headings as shown by standard and steering compasses. The course as shown by the Pelorus -will be the correct magnetic course that the vessel was heading on at the time she crossed the range. Then the difference between this correct magnetic course as shown by Pelorus and the course as shown -hy compass must he the devia- -tion, and this deviation corresponds to the ship's head correct magnetic and not ship's head by compass. As this is what is required in every case this simple pro- cess does away entirely with Napier's diagram of compass deviations, in' order to determine what the deviation would be were the ship to head correct mag- netic instead of by compass, which is attracted by the ship's iron, and instead of the ship heading as indicated by com- pass, may not be within 4 or 5 points of it. This is the most ser-ous difficulty with which the navigator has to deal in the use of his' compass. Where the deviations: are determined for different directions of the ship's head as indicated by compass and not by the ship's head herself; and where these deviations are large the application of the deviation corresponding to the correct magnetic course will only give an approximation (and hardly this in some cases) to the compass course, and it then becomes necessary to take the deviation corres- ponding to the approximate compass course and apply it to the correct mag- netic coutse to obtain the . compass course desired. Where deviations are very large it may be necessary to make several approximations before obtain- ing the desired compass course. As one can readily imagine, to do this, is a long and tedious job, requiring a_ great amount of figuring, besides many forms and operations to go through with. A HANDY METHOD, This method by Pelorus is handy and can be employed at any time; and rec- ommends itself to favor from its ex- treme simplicity and. comparative ease with which it is performed; not only this, but see the immense amount. of labor that it does away with in the em- ployment of rules, forms and figures in the plotting of the deviations as ob- served, drawing the curve to it, etc. all of which may tend to lead to error from the amount of figuring made necessary to arrive at results. The deviation as found for the ship's head correct mag- netic relieves the whole operation, thus simplifying and abridging the confus- ing and tedious rules and methods in common use, for it is the sh'p's head cor- rect magnetic that makes good the course as shown by compass. THE DUMB CARD MUST SHOW IT. _ It must be plain to see that if the sight vanes of the dumb card are so placed as to point out the correct mag- netic bearing of the range when in tran- sit (when the ship is in one with the range), the card must be pointing out the correct magnetic directions of the horizon, by means of the sight vanes kept to the range at time of transit, where the the fore-and-aft line meets the edge of the card must then be the correct mag- netic course of the ship's head: Whatever difference that the other compasses show in comparison with this correct magnetic course at that time, is the de- viation in each case. Taking the same deviation observa- tions as given in the Chicago example the work would stand as in the follow ing table. 1 ; 2 3 Ship's Head Deviation for by Pelorus Ship's Head or Ship's Ship's Head Correct Mag. Head Correct by Standard for Headings Magnetic. Compass. in Ist Column. Ne 120 WwW. North 12°) Wily: Ne 4 N by E (eines Ne 2 ks NNE Line Ne 37 8 NE by ,N 3% Ely Nevo 22 NE 7. a Ne 665 NE by E OU N81 ENE 1g N94. Ek E by N lowes N:106 £ East 16 . And so on with every point of the compass. To explain the foregoing. The first column represents the ship's head by | Pelorus, that is, what the Pelorus reads when the ship crosses the range with the sight vanes kept to the correct mag- netic bearing of the range at the time of crossing, and must therefore repre- sent the ship's head correct magnetic when the standard compass was on the points as shown by column 2. The sec- ond column shows the course that the vessel was steering at the time the ob- servations were taken; and the third column shows the deviation correspond- ing to the ship's head correct magnetic, as shown in column 1, and also the * deviation according to the ship's head in column 2. But, what is required to know is the deviation corresponding to the-ship's head correct magnetic, and al- though the deviation in the above table _is the same for the ship's head correct magnetic in one case and the ship's head by compass in the other; for ex- ample, when the ship's head is north, as indicated by compass the Dev. is 12 de- grees Wly, but when the vessel is head- - ing north by compass, she is in reality heading N. 12 degrees W., according to the correct magnetic points of the hori- zon. Thus, we can see at once that the Dev. for north by compass will not an- . swer for north correct magnetic; for on referring to column 1 it will be seen that correct magnetic north comes in somewhere between N. 12 degrees W. _and N. 4 degrees E., and that the devia- tion falls between 12 degrees and 7% de- grees. As we will soon see the Dev. cor- responding to correct magnetic north equals 814 degrees, so that by employing the Dev. corresponding to north as indi-