recorded all matters of importance occurring on board, such as meeting with vessels, carrying away of sails and spars, state of the weather, accidents to the crew, work progressing on board, etc., etc.

Half-way between midnight and midnight in the log-book (noon), will be seen the following headings, connected with red rulings: CourseDistance-Diff. of Lat.-Departure-Lat. by D. R.-Lat. by Obs.Variation-Diff. of Long.-Long. by D. R., and Long. by Obs.

We will now take them up in their order in dealing with them.

1st. "Course."-Having, perhaps, sailed several courses since the noon of the day preceding, the idea is (explained under heading of Dead Reckoning) to ascertain the bearing of the ship from the position of the previous day, which is considered as the "Course made good.”

2d. "Distance."-On the line of the bearing of the ship from the position last calculated to the point arrived at, the distance is considered as the "Distance made good."

3d. “Diff. of Lat."-In this space is to be entered the amount of latitude between the position last calculated and the position arrived at.

4th. "Departure."-Under this heading will be noted the number of departure miles (knots) the ship is either east or west of the place last recorded.

5th. "Lat. by D. R."-After applying the difference of latitude made, to the latitude of the ship on the previous day, we obtain the latitude of the ship by dead reckoning, and the same is marked under the above heading.

6th. "Lat. by Obs."-Latitude by observation is calculated at noon, and entered in this column.

7th. "Variation."-The variations used on the different courses are to be shown under this heading.

8th. "Diff. of Long."-The number of longitude miles made (estimated by using the middle latitude as a course in Table 2, together with the whole departure), finds a place here.

9th. "The Long. by D. R."-The longitude by dead reckoning is found by traverse table, by applying the difference of longitude made to the longitude of the ship's place on the preceding day.

10th. "Long. by Obs."-The longitude by observation at noon is calculated by chronometer sights worked either in the morning or afternoon, and then carried forward or back to noon by the employment of a traverse table.

NOTE.-See following page for form of log-book.

EXPLANATION.

Suppose that we should obtain a chronometer sight at 8 o'clock in the morning, and determine our longitude at that time. Between the time of this sight and noon 4 hours elapse, and, in order to ascertain our longitude when noon arrives, all we have to do is to correct the courses sailed since 8 o'clock, select from Table 2 the departure belonging to them, turn it into longitude miles for the parallel of latitude sailing on, and apply this difference of longitude to the longitude of the ship at 8 o'clock that morning.

Of course, this will not be exactly the longitude by observation, but it will be it so nearly that for practical purposes it can be considered as such.

Again, suppose that no observation was secured during the morning, but that a sight was obtained at 4 o'clock in the afternoon, and we wish to carry our longitude back to noon, in order to check the longitude determined by dead reckoning at that time, all we have to do is to find the departure, as before, that the ship has made since noon, and apply it to the longitude found by observation at 4 o'clock, P.M.

See the following examples:

TO CARRY LONGITUDE FORWARD.

At 8 o'clock in the morning, by a chronometer sight, the ship is in the longitude of 70° 30' West. She then sails S.E. (corrected course) 40 miles up to noon. Ship on the parallel of 41° North.

S.E. 40 miles, Table 2, gives 28.3 miles of departure.

28.3 miles of departure, parallel of 41°-38 miles of longitude.

At 4 o'clock in the afternoon, by a chronometer sight, the ship is in the longitude of 64° 50' West. She has sailed N.W. (corrected course) 50 miles since noon. Ship on the parallel of 38° North.

N. W. 50 miles, Table 2, gives 35.4 miles of departure.

35.4 miles of departure, parallel of 38°=45 miles of longitude.

The difference of longitude is subtracted from the longitude at 4 P.M., because at noon the ship was 45 miles to the eastward of her afternoon position.

Never ditto figures in the log-book.

Where the same course and wind is continuous, always use ditto marks.

CHARTS.

SIGNS AND ABBREVIATIONS USED, SHOWING QUALITY OF BOTTOM.

Buoys are marked: B. (black); Cheq. (chequered); H. S. (horizontal stripes); R. (red); W. (white); B. W. (black and white); B. R. (black and red); R. W. (red and white); V. S. (vertical stripes).

A green buoy indicates the position of a wreck.

BUOYAGE ON THE COAST OF THE UNITED STATES.-In approaching a channel from seaward, leave red buoys with even numbers on the starboard, and black buoys with odd numbers on the port. Buoys painted with red and black horizontal stripes mark obstructions with channel ways on either side.

Buoys painted with black and white perpendicular stripes mark a midchannel and must be passed close to to avoid danger.

Lights are indicated by a dot, colored yellow, with a red spot in the middle; (if there is any uncertainty about its character it is simply marked Lt.); Lt. F.-light fixed; Lt. Fl.-light flashing; Lt. Int.-light intermittent; Lt. Rev.-light revolving; Lt. F. and Fl.—light fixed and flashing; Flg. Lt.-floating light; Lt. Ves.-light vessel; the color of the light is expressed in full, as red, blue, green, white, red and white, white, red and green; when no color is expressed it is taken to be white.

Currents are indicated by a feathered arrow, and the direction of the arrow shows the direction of current.

Flood tide stream is shown by an arrow feathered on one side; ebb tide stream by unfeathered arrow.

Rocks just under the water are indicated by a small dotted circle, with cross in center; rocks awash, or just above water, are indicated by a dotted circle, with a dot or dots in center; a dotted circle with a numeral in it, signifies a shoal, with the feet or fathoms of water over it. Rock, island, or shoal, with E. D., signifies existence doubtful; P. D., position doubtful, though known to exist.

TABLE OF DISTANCES

at which objects can be seen at sea, according to their respective elevations and the elevation of the eye of the observer.