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RE Ta aga opposite corner. Next saw through on the line and either half,. or piece, is the figure wanted. This can be done much better with three laths. Make a perfect square with two of them by nailing the ends - together. Where they are fastened will be the right-angle. Both laths must be ex- actly of the same length from corner to the ends. Take the third lath and lay it from the end of one to the end of the other and fasten it by nailing. This lath must be laid along the outer end of each of the other laths. When this is done there will be a little of the inner edge of each lath projecting over the third 'lath.. Trim this down even with the lath over which it pro- jects. "The third lath represents the hypotenuse of the figure; the other ° .two the equal sides. This figure will be -some. four feet high,. and will prove very. serviceable and .easy to work with on account of its size. a» East. =» A 3+POINT BEARING--ISOSCELES TRIANGLE EXAMPLE. Let A be a ship steering east; B a light- house bearing three points on the port bow, that is NE by E. She proceeds on her course till the light bears three points to the left of NE by E, that is NNE, then CB is equal to CA, or the distance traversed: from A to C is the same distance as C to B. The angle at A and the angle at B are equal, therefore, the sides op- posite these angles are equal. CROS S-BEARINGS, _ The method of cross-bearings to- find the ship's place is a good one, since under certain conditions it is the only one that can be employed. Its chief merit is that current and leeway cannot take effect since both bearings are taken simultaneously. But the great trouble with this method is that it requires two fixed objects marked on the chart. to be found along every coast. The These are not always. TAe Marine REVIEW bearing requires plotting "oa" therchart, and in order to do this the compass bearings have to be converted into true bearings by allowing for Var. and Dev.--Ely. to the right, Wly. to the left of the compass bearing. Re- member that the Dev. to be used is for ship's head and not the Dev. cor- responding to the direction of the bearings. This is another drawback to the method, but for accuracy it cannot be beat. The method is as follows: -Observe in quick succession the compass-bearings of two lights (or other stationary objects which are de- finéd on the chart), so far apart that each will bear close to 45 degrees off the ship, but in opposite directions. Then refer to the chart, and by the aid of the parallel ruler and either the magnetic or true roses (if the former is used no correction is to be made for the variation in. that lo- cality, 'but-if "the true rosé is'*em- ployed the variation must be applied in order to convert it into a correct magnetic bearing), draw pencil lines through the objects in question, ac- cording to the respective bearings of the two objects, and the points where the lines cross will show the position Sighting through an azimuth attachment. bb are the upright arms or sight vanes of the in- strument. The dotted line from the eye to A shows the instrument in use for direct bearings of distant objects, or of a reflected bearing of the sun when partially obscured, and consists of a plain mirror, hinged, sight vanes, and prism, arranged as in the figure; t- shows the reading on the compass. of the ship at the time the bearings were taken. It 'is to be understood that the compass bearings are to be corrected for ithe deviation (if any exists) of the ship's head at the time the bear- ings were taken, so as to convert them into correct magnetic bearings before applying the lines to the chart. The nearer the bearings are to a right-angle the more accurate the po- sition will be defined on the chart.: The bearings should not be more than 120° and not less than 60°. SCALENE TRIANGLE BEARING, Each side of a scalene triangle bearing is unequal. This is a very useful bearing, and like all the other bearings that have been mentioned, except the cross-bearing, affords the means of locating the vessel by two compass-bearings of the same object when in sight of land, where only a 29 | siffgle" light, Headland, or other fixed feature is to be seen. This scalene bearing has to be plotted on the chart, and the bearings and course have to be corrected for Dev. and Var., and here is where it loses its charms. However, it is well worth knowing. Rule----Observe the bearing of the object and note the time. After hold- ing the course until: the object has changed its bearing at least two or three points, note again its bearing and the time, and calculate the dis- tance the vessel has run in the inter- val between the first and last bear- ings. Trace the two lines of bearing on the chart in pencil, then span the dividers to the distance run, and pro- ceed as follows: With the parallel ruler set to the course (over a chart compass dia- gram) sailed by the ship between bearings, move them toward the pen- cil lines until both points of the di- viders, held against the beveled edge of the ruler, just fits across the lines, and these two points where the divid- ers rest will show the position of the vessel at the time of the first bearing | as well as her place at the time. of. © the second bearing. The two compass-beatings must be corrected for the deviation, as well as the variation (if any exists) of the ship's head at the time the bearings are taken, so as to convert them into true bearings before tracing them on the chart. The compass course must also have the variation and deviation applied thereto in order to reduce it to a true course before: setting the parallel ruler. by the compass rose on the chart. © THE OTHER DODGE BEARING, Here is another dodge bearing, which is as follows: When an object on shore is abeam, note the time and distance run until the object changes its bearing 2%4 points. Twice the dis- tance run in the interval is the dis- tance from the object. In the dodges no allowance is to be made for Dev. "Ne