less than six points of the wind, but small ones will often lie within less than five points. To determine the point towards which the ship actually moves under such circumstances, it is evident that the leeway must be allowed from the wind, or towards the right of her apparent course, when she is on the larboard tack, but towards the left when she is on the starboard tack.

The leeway made by a ship at sea may be estimated by drawing a small are of a circle at the stern, and marking on it the points of the compass. The angle between the fore and aft line of the ship and the track left by the ship on the sea, or the wake, is the required leeway. This angle may also be observed by a mariner's compass placed at the stern.

In estimating the leeway mariners are often guided by certain general rules, which we here subjoin, as they may be useful in the dark, when the leeway cannot be known from observation. These rules, however, must be considered as affording only a rough approximation.

General rules for estimating the leeway, when a ship is close hauled.

1. When the water is smooth, all sails set, and the wind moderate, allow no leeway; but if there be a strong breeze the leeway may amount to a point.

2. When the top-gallant sails are handed, the leeway may be from one point to one point and a half.

3. Under close reefed top-sails, the allowance may be from two to three points.

4. With top-sails handed, from three to four points.

5. Under courses, from four to six points, according to circumstances.

6. Under reefed courses, possibly six points. 7. Under storm stay-sails, possibly seven points.

8. Under bare poles, from seven to eight points.

Much in any case must be left to the judgment of the mariner, and he must take into account a variety of circumstances, in making allowance for leeway, before he will venture to affirm that his estimate is entitled to entire confidence.

The leeway and variation being supposed known, we have now to show how the allowances are made for them in actual practice.

Rule.-Put down the variation, and mark it R or L, according as it is east or west; and underneath put the leeway and mark it R or L according as the ship is on the larboard or starboard tack, take the sum when they are alike, and the difference when they are unlike, and work it with the name of the greater. Then if the result is marked R, allow it to the right, if L, to the left of the compass course, and you have the

true course.

Example 1. Compass course N. W. W., variation three points west, leeway two points, ship on the starboard tack; required the true course? Here variation three points L, and leeway two points L, therefore the total correction is five points towards the left; whence the true course is W. by S. S.

Example 2.-Compass course S. E. by E. on the starboard tack, with three points leeway, and

ON KEEPING A SEA JOURNAL.

A sea journal contains an account of every tning of importance that occurs on ship board, and in particular a minute detail of every thing connected with the navigation of the ship; to enable the mariners at any time to find her true situation.

For

On commencing a voyage, the true course to the place it is first intended to reach is either taken from a chart or computed, and thence by allowing for the variation the corresponding course by the compass is known; and, if circumstances admit, the ship is kept upon that course. When a ship leaves the land the bearing of some known place is taken by the compass, and its distance in general estimated by the eye; and that distance is considered as the first distance sailed, with the opposite bearing as a course. But the distance may be accurately computed if the bearing of the object be taken twice, and the ship's course and distance in the interval be accurately noted. let a ship sail from B to C (fig. 2), and note at these points the bearing of the object A, then the angle A is the change in the object's bearing, the angle B the angle included between the bearing of A at that place, and the ship's course, and the angle C, the angle included between the bearing of A at C, and the opposite point to the course. Now sin. A sin. B:: BC: AC, and sin. A sin. C::CB: AB; that is, as the sine of the change in the object's bearing is to the sine of the angle included between the bearing of the object at the first observation, so is the distance run in the interval to the distance of the object from the second place of observation.

The other courses and distances made during the day being determined by the compass and the log, they are written in chalk on a black board, called the log board, of which we shall shortly show the general form, and afterwards copied into a book ruled in the same manner, called the log book. The courses are either corrected for leeway before they are entered on the board, or the leeway is also entered with the course in a column appropriated for the purpose. The setting and draft of currents, the estimated effect of the swell of the sea, &c., are also entered in the column of remarks, a column which contains a record of every circumstance of importance whether connected or not with the navigation of the ship.

The setting of the current is considered as a course, and its drift as a distance, and the opposite point to that in which a swell of the sea comes is considered as a course, and what the ship is presumed to drift by it as a distance. If the course is changed during the hour, an estimated course for the whole hour is commonly entered on the log book.

In lying to, the middle course between the points on which the ship comes up and falls off is taken as the compass course.

The courses in the log-book being corrected for leeway and variation, and the distance on each course summed up and entered in a traverse table, including among the courses and distances the effects of currents and the swell of the sea; the place of the ship is determined by the methods already given under the different heads of navigation; but the computations are generally performed, and they may be exactly enough performed, by inspection.

The finding of the ship's place, from the courses and distances marked on the log-board, is called working a day's work. An abstract of the whole, containing the course and distance made during the day, the difference of latitude and departure, the latitude and longitude obtained from the reckoning, and those deduced from observations, and the bearing and distance of the port, or of the nearest land that may lie in the ship's

way.

If the variation is given in degrees it will be found convenient not to correct each course separately for it, but to find the resultant in course and distance for the whole day's work, allowing only for leeway; and then with this distance, and the resulting course corrected for variation, find the true difference of latitude and departure. The day is divided, according to the civil mode, into two intervals of twelve hours each, the first marked A. M., the latter P.M. It is supposed to begin at midnight, though the reckoning is worked up from noon to noon, and the place of the ship settled each day at that time.

We shall now exemplify what has been said on the method of keeping a journal, by two days' work, in which a ship is supposed to take her departure from Cape Finisterre, and bound for Madeira. The course being found each day to Porto Sancto. Ten fathoms are accounted to

the knot.

As Cape Finisterre on taking the departure bears N. N. E., the compass course from it is S. S. W., and one point three-quarters west variation being allowed to the left makes the true course S. W., and the distance is fifteen miles. The second course S. W. W. corrected in like manner for variation is S. S. W. W., and the distance as summed up on that course is 18.7 miles. The third course S. E. S. corrected for variation is S. E. by E., distance till six, 18-3 miles. At six the ship begins to make leeway, to the extent of half a point; and, as she is on the starboard tack, both leeway and variation are to be allowed to the left. The sum of them one point three-quarters and half a point is two points one-quarter, which allowed to the left of S. E. S., the course which the ship was steering, gives S. E. by E. E. for the true course, and the distance till eight, 14.9 miles. From eight till nine, and so on till midnight, the ship ran W. W. on the larboard tack, making half a point leeway. Hence we have variation one point three-quarters east, and leeway half a point east; difference to be allowed to the left one point and a quarter; and this allowed to the left of W. N. gives W. S. for the true course, and the distance is 27.8.

On Feb. 10th A. M. the first course is S. S. E. on the starboard tack, with variation 1 L, and leeway L; sum 24 left, and true course S. E. ↓ F. distance till five, 32.3 miles; the second course is W. by N. on the larboard tack, 14 leeway R. whence 1 L-1R point, left, the correction; and the true course is W. N. and dis tance 46.9. The swell coming from N. N. W. will drive the ship S. S. E., on which course 14 variation being allowed to the left, the true course S. E. 4 S. distance nine miles.

The first course on Feb. 10th, P. M. is S. E. by E. on the starboard tack, with 14 points leeway. Hence 1 L + 1} L = three points L. the correction of the course which hence is E. and the distance till four, 25.1 miles. The second course is W. S. W. W. on the larboard tack with 1 points leeway; therefore 13 L.1 R. point left; whence the true course is W.S. W. and distance thirty-nine miles, the leeway being different the next hour. The correction of the next course is 2 R.-1} L. =

R. which allowed on W.S. W. W. gives W.S. W. W. for the true course, distance from five till eight, 16:3 miles. The last course P. M. Feb. 10th is E. by S. on the starboard tack with two points leeway. Hence the correction is

2 L.+14 L. 3 L.; whence the true course is N. E. by E. E. distance from eight till midnight 24.4 miles.

The first course Feb. 11th, A. M. is west, on the larboard tack, two points leeway: hence 2 R. — 13 L. R. and the course is therefore W. N. and the distance till two, when the leeway changes, is 11.6 miles; at two the course steered is the same, but the correction is 4 R. 14 L. 21 R. which allowed to the right of W. gives N. W. by W. W. for the true course, and the distance in that with four points leeway; hence the correction is 4 L. + 1} L. = 5% left, distance till six 10 miles. At six with the same course, and on the same tack there are five points leeway, whence the correction is 64 L. and the true course E. by N. N. and the distance till eight 16.6 miles. At eight the course is W. N. W. on the larboard tack with five points leeway, whence the correction is 5 R.—1 L. = 34 R., and consequently the true course is N. N. W. W. and the distance till noon 17.6 miles.

Note.-The distances marked opposite any hour are those given from the hour preceding till that opposite which they are entered.

Collecting now the courses our distances from noon of Feb. 9th, till noon Feb. 10th, into a traverse table, we have it as under.

With the diff. lat. 77-64 S. in its column, and dep. 21.22 W. in its column, the course and distance will be found in a table of diff. lat and dep. to be S. 15° W. 80.5. With this course and mer. diff. lat. 105 in lat. column, the diff. long. will be found in the dist. column to be 28.7, or with mid. lat. 421° as a course, and dep.. 21-22 in lat. column, the diff. long. will be found 28.7 in the dist. column.

By computation. As diff. lat. 77.64: dep. 21.22 rad. tan. 15° 17', the course. As rad. : diff. lat. : : sect. course: 80-49, the dis

Mer. parts

2103

Mer. diff. lat.

647 S.

Long. in

9° 45′ W.

Diff. long

6 32

= 392 W.

With mer. diff. lat. 647 S. in lat. column, and diff. long. 392 W. in dep. column, the course is S. 31°W.; with this course and proper diff. Jat. 513 in lat. column, the distance is found 600 miles.

Or with mid. lat. 37 as course, and diff. long. 392 as dist. the dep. is found 311, in lat. column. Then with diff. lat. 513, and dep. so found, 311, in their proper columns, the course is found S. 314 W. and distance 600 miles.

By calculation, by Mercator's sailing. As mer. diff. lat. 647 diff. long. 392 :: rad. : tan. 31° 13', the course.

As rad. diff. lat. 513:: sect. course 31° 13': 600, the dist.

By middle latitude sailing

As diff. lat. 513: diff. long. 392: : cos. mid. lat. 37° 27′ tan. 31° 14′ the course.

:

As rad. diff. lat. 513 :: sect. course 31° 14': dist. 600 miles.

The corrected courses from noon of Feb. 10th till noon of Feb. 11th, being with their proper distances collected in like manner, we have the following traverse table :—