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correct bearings from? We might -be leaving a Lake Erie port, bound for the Southeast shoal. For example we will say that we have just left Ash- tabula. On coming out the piers we find that our compasses are not heading correctly. The chart shows that we should head north half east when parallel with the piers. We now wish without delay to shape a perfect course to the Southeast shoal. Our new method (new to the most of us) will now furnish us with the means for finding the error of our compasses in just as' certain as with the ranges. Before setting wp our instruments for use we must also know just what variation of the compass means, We have shown that Deviation of the compass needle is caused by dis- turbing influences aboard the boat. Variation of the compass needle is caused by disturbing influences in the earth. Even if your compass is per- fect sand. shows. No. etior tierce ar very few places on ithe earth where it will point exactly north. We do not need to find this variation ourselves. Government officials find it for us and supply us with tables or charts that show us just the amount of variation at each place. At Cleveland the north point of the needle is drawn three de- grees to the west, at Buffalo six de- grees to the west, at 'Chicago three a way degrees to the east and so on. In. taking bearings of ranges or in mak- ing courses we do not need let the two terms (deviation and variation) cause us to get mixed. All courses and bearings given in government 'books and on charts are true--that is, the variation has not been allowed. When you correct this bearing or course for variation you then make it a magnetic course or bearing. A magnetic course means a course that can be made good by a perfect com- pass. Our government books and charts. might very easily give us mag- netic courses and bearings and then we would not thave to 'bother so much about variation. However, several writ- ers of lake pilot books have turned these true courses and bearings into magnetic courses and bearings and we find it very convenient. When we want to find the magnetic bearing of a certain range we simply have to look up the name of this range in the book and do not have to bother about variation at all. The Deviation of our compass is all that we need then bother about. But if we get the bear- ing of a range from the light-house book or from a chart we must find the variation of the compass at that particular point. We then apply it in "TAE. Marine. REVIEW just the same manner that we do de- viation. If it is easterly variation we allow to the left and if it is -westerly we allow to the right. You must thoroughly understand the difference between variation and deviation. Fon example we will say that we wish to find the error of our compass 'On a range that we are coming to. If we have no book or deviation card that shows just what the correct magnetic bearing of that range really is we must find it either on 'the chart or in the light-house book. By referring to either of these we find that they give a bearing of north 'by east. We must now find the variation for this locality. We will say (for example) that our varia-. tion chart shows us the variation at % 33 locality where there was a different - variation and you would ibe as badly off as ever. A compass adjuster can | adjust your compass for deviation. but he can't for variation. If your compass needle is pulled to one side by some steel or iron a magnet can be fastened close to the other side... of your compass so that it will draw back the needle to where it .should -- be. If. iron aboard the ship puis your compass needle to one side on Lake Erie it does the same thing on any other lake. But magnetism of, the earth causes. the variation of the compass. At Buffalo the earth causes the needle to vary about 5 degrees to the west while at Duluth it causes it to vaty about 6. degrees (5 the east. this place is 5 degrees easterly Maps to show you the. variation ae (practically a half point). We allow different points are made like this: ° 9 SEO 6oW f >' Sw 3 4w Sw . ee | \ | are ers Lo x / cag ES BUFFALO mat CER, @ LNG ee ie TOLEDO ¢ A, ~ i 3 ; : ae ; -- 1 ee a FAIRPORT CLEVELAND! 5s | fey ZW this to the left and change our range into a bearing of north half east. If we now headed our boat on this range..and. found. that our compass showed exactly north half east we then have perfect compasses. When courses and bearings are marked 'corrected' or "magnetic" you don't have to allow for variation. This has already been allowed and a perfect compass will follow them exactly. .If your compass has error (or deviation) you can follow these the courses by allowing for error, But if courses and 'beatings are marked "True you must. and. tie variation given for this locality and allow for it in order to make a course that a perfect compass will follow. The variation on the Great Lakes is not so great as it is in some other parts. of the world. The greatest variatiom here is about one point westerly at the east end of Lake Ontario. At some points it disap- pears altogether. But there are places on the earth where the compass points east and west instead of north and south. : There would be no use trying to make a compass show true north by the use of an adjusting magnet "be- cause the boat might soon sail into a bearing. 4° This map shows the variation at different points on Lake Erie. You will notice crooked lines crossing the lake, each with a.mnumber at éach end. You will notice that the line passing through. Cleveland has 3°W at each end. This means that at any place. along this line there ate 36 degrees westerly variation. Fairport is about half way between -the lines marked 3°W, and 4°Wi Therefore the variation at Fairport would be 314° West. But in allowing for varia- is hardly necessary to get Use the near- tion. it down to half degrees. est full degree. Now suppose you wanted to shape a course from Buffalo to the west end of the lake. Your course will then pass through every line of varia- tion shown on the lake. You would then have to strike an average varia- tion. Add them all together--6, 5, 4, 3, 2. This would 'make 20°)- Then > since there are 5 lines you *must divide by 5. This would give you an average variation over the whole course of 4 degrees westerly. In taking bearings of the heavenly bodies the 'bearings given in the 'book are "True" therefore you 'have to allow the variation to get a magnetic