cisely identical in form, and at the same time independent of each other, so that the first may be worked as soon as the observation is taken; and as few logarithms are required, and as there is but very little addition or subtraction of arcs, the computation may be completed very expeditiously, and with less liability to error than in the more lengthy methods.

TABLE OF CORRECTIONS FOR ABBREVIATING DOUBLE ALTITUDES, THE REDUCTION TO THE MERIDIAN, &c.

Multiply A by the Time, and B by the Declination.

ON THE USE OF THE TABLE.

Enter the table with the declination and hour-angle, and take out A and B. Multiply A by the minutes in the hour-angle, and B by the declination, marking the former correction, the latter +.

Example.

Given H.A. 30m. 10s., Dec. 10° N.: to find arc (a) and arc (1).

Here, Dec. 10 gives 9 sec. for A; and H.A. 30 min. gives ⚫5 for B. Multiplying 9 by 30, and 5 by 10, the corrections are - 27 sec. and + 5'.

TO FIND THE LATITUDE AND LONGITUDE BY TWO ALTITUDES

OF THE SUN.

Both observations are supposed to be taken within an hour and a half of noon, and at a sufficient interval to ensure, if possible, a difference of not less than 1 or 2 points in the bearings. The longitude by dead reckoning should not be more than 40 or 45 miles in error, and it is to be used in finding the hour-angle at each observation. This hour-angle and the declination are to be corrected by the elements taken from the Table. The remaining portion of the work is best explained by the following examples:—

Example.

In lat., by account, 45° N., long. 10° 0′ W., the following observations were taken; to find the ship's position :—

On the meridian of 10° W. on the chart, are marked latitudes (1) and (2). The position lines, at each observation, being drawn through these points, intersect in lat. 44° 59′ N., long. 10° 26′ W., which is the place of the ship.

Example II.

In lat., by account, 50° N., long. 10° 20′ W., the following observations were taken to find the ship's position :

Example III.

In latitude, by account, 52° N., long. 20° 26′ W., the following observations were taken to find the ship's position :

On the meridian of 20° 14′ W. are marked latitudes (1) and (2). The position lines drawn through these points intersect in long. 20° 32′ W. Hence, the ship's position is lat. 52° 0' N., long. 20° 32′ W.

NOTES.

1. To find the Hour-Angle.-To the G.M.T., by chronometer, apply the equation of time, with its sign from p. 1 (Nautical Almanac) the result is G.A.T. To the latter apply the longitude in time, adding in East longitude, subtracting in West: the result is the hour-angle.

N.B. If the hour-angle is less than 24 h., subtract it from 24 h.; if greater, subtract 24 h. from it.

2. Whether to take the sun or difference of arcs (1) and (2) is easily seen by reference to the latitude by account; with which the latitude by observation must be made to agree. Or thus: When latitude and declination are of the same name, take the sum of (1) and (2); when of different names take their difference. Also, if the ship is between the sun and the equator, take their difference.

3.—If latitude (2) confirms latitude (1) no further work is necessary, and the position of the ship is satisfactorily determined.

4. The first observation may be worked as soon as taken, and the second part of the work follows the same order as the first.

5.-The latitude alone may be found by a single observation, if taken within 30 or 40 minutes of noon.

6.-When an altitude near the meridian and the meridian altitude can be taken with any degree of accuracy, the ship's position may be found as in Example III.

7.-The bearings at each observation are to be taken from an azimuth Table. The position lines are at right angles to these bearings.

8. The longitude by D.R. is only required roughly. The longitude corrected for run must be used in finding the second hour-angle.

(To be continued.)

[In going over the above simple and ingenious methods we find that the results obtainable can only be regarded as approximate, and that in rare instances will they be found strictly accurate. We have, however, much pleasure in publishing them on the authority of so good a navigator as Mr. Johnson, leaving it to the seaman to test their accuracy.-Ed. N. M.]

GENERAL AVERAGE.

YORK AND ANTWERP RULES.

A review of the progress made since the date of the Antwerp Conference of the Association for the Reform and Codification of the Law of Nations in September, 1877, in obtaining the adoption of the York and Antwerp Rules.

By SIR TRAVERS TWISS, Q.C., D.C.L., &c., Chairman, and H. D. JENCKEN, Barrister-at-Law, Hon. Secretary, of the Committee on General Average.

HE past year has not been barren in its results as regards the labours of the Association for the Reform and Codification of International Law, and the English Central Committee for effecting a unification of the laws regulating General Average losses. After some short delay, the General Shipowners' Association were induced to take action, and ac