APPENDIX IV.

BRITISH BOARD OF TRADE INSTRUCTIONS RELATING TO THE MEASUREMENT OF SHIPS, 1913.

61861°-13-19

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NOTE. This edition supersedes the edition issued in 1907. The contents have been rearranged and to a large extent rewritten; and the printed circulars and other instructions issued since 1907 have been embodied.

PART I.-MEASUREMENT OF BRITISH VESSELS.

PRELIMINARY.

1. Authority for instructions.-These instructions are issued by the Board of Trade under the provisions of the Merchant Shipping Acts for the assistance and guidance of their officers in measuring the tonnage of ships.

2. Fees and expenses.-Instructions as to the fees and expenses payable in connection with tonnage measurement are contained in the pamphlet entitled "List of fees and expenses payable in connection with Board of Trade surveys."

3. Law relating to tonnage.—The tonnage regulations of the Merchant Shipping Acts, 1894 to 1907, are inserted in Appendix 3, page 271, and the surveyors are expected to make themselves thoroughly conversant therewith, and also with the following instructions regarding their application. Whenever in the course of these instructions reference is made to "the act" or to a section or schedule by number only, the reference is to the Merchant Shipping Act, 1894. 4. Surveyors to refer to principal surveyor for tonnage.—The measuring surveyor will in all cases obey and be immediately responsible to the principal surveyor for tonnage with regard to these instructions, and when in doubt upon any point he should refer it to him for direction, and the principal surveyor will, if necessary, submit it for the consideration and decision of the Board of Trade.

5. Gross and net tonnage.-For the purpose of the tonnage regulations of the Merchant Shipping Acts, the ton is a unit of volume containing 100 cubic feet. The act provides that

for the purpose of ascertaining the register or net tonnage of a ship, the gross tonnage shall first be ascertained in accordance with the directions contained in the second schedule, and the deductions provided for in the acts shall then be made from the gross tonnage so ascertained.

GROSS TONNAGE.

6. Items of gross tonnage. The gross tonnage consists of the sum of the following items: (a) The cubical capacity of the vessel below the tonnage deck;

(b) The cubical capacity of each space between decks above the tonnage deck;

(c) The cubical capacity of the permanent closed-in spaces on the upper deck available for cargo or stores or for the berthing or accommodation of passengers or crew; and

(d) The "excess of hatchways."

7. Application of Rules I and II, respectively. The act provides that the gross tonnage must always be ascertained by Rule I in the second schedule, except in the case of ships which requiring to be measured for any purpose other than registry have cargo on board, and ships which requiring to be measured for the purpose of registry, can not be measured by Rule I, in which cases Rule II may be employed. The surveyors should note, however, that Rule II is not to be adopted in any case without the special sanction of the Board of Trade, except in the case of pleasure yachts under 50 feet in length, which may be measured for registry under Rule II without special authority if the application of Rule I is impossible owing to some or all of the fittings of the vessel being in place at the time of measurement.

Any ship which has been measured under Rule II may at any subsequent period be remeasured under Rule I on the application of the owner, and the payment of the prescribed fees.

MEASUREMENT UNDER RULE I.

SPACE BENEATH THE TONNAGE DECK.

8. Definition of tonnage deck. The tonnage deck is the upper deck in all ships which have less than three decks, and the second deck from below in all other ships; but the protective deck of a warship is not to be considered as a deck within the the meaning of section 77 (6).

9. Modification of rules for vessels with double bottoms.-The rules for measurement under the tonnage deck are contained in paragraphs (1) to (3) of Rule I, but in the application of these rules to vessels with double bottoms for water ballast regard must be had to the provisions of section 81 in respect of the depth measurements in every case. In the case of vessels in which the double bottoms are designed with a rise transversely, regard must also be had to the modifications made by the Board of Trade under section 77 (7) to meet such cases in respect of the position and number of breadths to be measured, and the mode of computing the areas. The rules as modified under these sections are printed on pages 276 to 278, and must be followed in all cases so far as they apply.

10. Measurement to be made at an early stage.-In order that the measurement of the gross tonnage may be effected under proper conditions, the surveyors should watch the progress of the building of all steam vessels within the limits of their port, so that the measurements may be taken when the hold is ready and while it is still sufficiently clear for the purpose. At the same time, it will be understood that the responsibility for applying for measurement rests with the builders or owners, as the case may be.

11. It is of great importance, not only that the rules given by the act should be followed, but that all the required measurements should be taken, and the calculations made, in one uniform and correct manner, so that one general system may prevail in this respect throughout the various ports of the Kingdom. For this purpose the following practical directions are given, showing the several progressive steps, briefly stated, to be observed in the practical operation of measurement by Rule I.

The measurements made at the ship may be recorded in the notebook provided for the purpose (form surveys 58A), and they are subsequently to be entered in the printed formula appropriate to the case. (See par. 42, and p. p. 299.)

12 Length. The length at the tonnage deck, in all vessels of the usual sheer 1, is to be taken on the upper surface of the deck, at such a parallel distance from the middle line of the ship as to clear the several hatchways and other obstacles that may present themselves. Having fixed upon the ends of this parallel line as far, both forward and aft, as may be found convenient, mark them on the deck, and square them into the middle line of the ship; then take the distances from the points thus determined on the middle line to the inside of the plank at the bow and stern, respectively, or to the inside of the angle irons or frames in iron or steel ships if not ceiled at bow and stern, making the requisite deductions for the rakes of the bow and stern, as set forth in the rule, and as shown in figure 1; the sum of these two distances, added to the length of the parallel line marked on the deck as aforesaid, gives the whole length required. 13. Points of division of the length or stations of the transverse areas.-Having divided the length into the number of equal parts required by the rule, set off the points of division by markFIGURE I. Showing the length of a vessel at the tonnage deck, its points of division for the stations of the areas, and the depth at each area, as measured under Rule I (1) .

D, D (dotted line), the length, taken on the upper side of the deck from plank to plank, showing the deduction at each end (namely, the distance from the inside plank to the upright dotted line at D), as prescribed by the rule, on account of the rakes of the bow and stern. These deductions are necessary in consequence of the length being taken above its right position; the right position being at the head or top of the areas, shown by the dotted line passing through the points C, C, etc., at one-third of the round of the beam below the deck line.

The length, being in this case 112.75 feet, is divided into six equal parts, giving the stations of the areas, with the common interval of 18.79 feet between them.

Cd, Cd, etc., represent the stations and depths of the areas of the five points of division.

C, C, C, etc., show the upper points of the depths at one-third of the round of the beam below the deck or beam line.

d, d, d, etc., show the lower points of the depths, at the upper side of the ceiling at the inside of the limber strake.

ing their places on the tonnage deck with a piece of chalk (thus showing the positions of the different transverse areas on the tonnage deck), and number them successively 1, 2, 3, 4, etc., No. 1 being at the extreme point of the length at the bow, No. 2 at the first point of division just marked on the deck, and so on successively, the last number being at the extreme point of the Ingth at the stern. (See Fig. I.)

14. The positions at which the areas have to be taken are next to be transferred from the deck to the keelson in the hold, and for this purpose a line is to be extended down the main hatchway in a direction perpendicular to the keel, by means of a square placed on the upper side of the keelson; the distance of the midship area from this line at the tonnage deck is then to be set off from the point thus determined on the keelson, which gives the station of the midship area on the keelson; and the stations of the others are obtained on the keelson by setting

1 It is found that the length taken on the surface or sheer line of the deck, in vessels of the usual sheer, is as eligible for the practical purposes of tonnage as when taken on the perfect straight line or chord of the sheer; for the difference in the two lengths thus taken, in the case of a vessel having more than the usual sheer of 3 feet in 250, amounts to about 24 inches, giving a difference in the tonnage of only about one-tenth per cent.

But in the case of the Dutch galiots, or doggers, as they are termed, which have a depth of sheer of about 5 feet in 100, the difference in the two lengths amounts to about 11 inches, giving an increase of about 1 per cent in the tonnage due to the increased length. Therefore, in all such cases of unusually large sheer, the length for computation must be taken by means of a tape or line stretched tightly from end to end of the deck.