Domes, skylights, and airshafts shall be exempt from measurement. When there is an opening in the floor of a superstructure immediately below a skylight, the exemption shall include the space between the skylight and the opening in the floor of the superstructure immediately under the skylight. The remainder of the superstructure shall be included in the measurement. The space, in addition to the skylight, that may be exempted by this section is that indicated by A, B, C, D in Figure 12, which follows.

FIGURE 12.-Open spaces between skylight and

opening. Skylights

Rooms receiving light from Skylights

SPACES AVAILABLE FOR PASSENGERS NOT TO BE EXEMPTED

§ 135.111 Spaces for use of passengers not exempted.

Spaces for the use or possible use of passengers shall not be exempted from measurement except as stated in § 135.82

(a).

135.112 “Passengers" defined in case of army and navy auxiliary ships. In case of army and navy transports, colliers, supply ships, and hospital ships, as defined in §§ 135.1-135.3, the terms "passengers" shall include all officers, enlisted men, and other persons who are not assigned to duty and who are not duly inscribed on the ship's rolls. SYSTEM FOR MEASUREMENT OF CUBICAL CONTENTS OF SPACES INCLUDED IN GROSS TONNAGE

§ 135.141 Use of Moorsom system as applied in any country in measuring vessels for national registry.

The cubical contents of the spaces included, by this part, in gross tonnage may, in any country where the Moorsom system of measurement has been adopted, be ascertained under that system as applied in measuring vessels for

national registry, provided that system is substantially similar to Moorsom system of measurement as set forth in §§ 135.142-135.241.

§ 135.142 Use of Moorsom system as set forth in this part.

In countries that have not adopted the Moorsom system of measuring spaces within vessels, the cubical contents of any of the spaces included in gross tonnage shall be ascertained according to the Moorsom system as set forth in the following sections: §§ 135.171-135.182 for the measurement of empty vessels; §§ 135.211-135.213 for laden vessels; § 135.241 for open vessels.

RULES FOR MEASUREMENT OF GROSS
TONNAGE OF EMPTY VESSELS

§ 135.171 Length taken on tonnage deck.

The length for the admeasurement of ships having one or more decks is taken on the tonnage deck, which is:

(a) The upper deck for vessels having one or two decks.

(b) The second deck from below for vessels having more than two decks. § 135.172 Measurement of length, in general.

Measure the length of ship in a straight line along the upper side of the tonnage deck from the inside of the inner plank (average thickness) at the side of the stem to the inside of the midship stern timber or plank there, as the case may be (average thickness) deducting from this length what is due to the rake of the bow in the thickness of the deck and what is due to the rake of the stern timber in the thickness of the deck, and also what is due to the rake of the stern timber in one-third of the round of the beam; divide the length so taken into the number of equal parts required by the following table, according to the class in such table to which the ship belongs:

(a) Class 1. Ships of which the tonnage deck is, according to the above measurement, 50 feet long or under, into four equal parts.

(b) Class 2. Ships of which the tonnage deck is, according to the above measurement, above 50 feet long and not exceeding 120 feet, into six equal parts.

(c) Class 3. Ships of which the tonnage deck is according to the above measurement, above 120 feet long and

not exceeding 180 feet, into eight equal parts.

(d) Class 4. Ships of which the tonnage deck is, according to the above measurement, above 180 feet long and not exceeding 225 feet, into 10 equal parts.

(e) Class 5. Ships of which the tonnage deck is, according to the above measurement, above 225 feet long, into 12 equal parts.

§ 135.173 Measurement of length in case of break in double bottom.

In the case of a break or breaks in a double bottom, the length of the vessel is to be taken in parts according to the number of breaks, and each part divided into a number of equal parts according to the class in the above table to which such length belongs.

§ 135.174 Finding of transverse area of ship at each point of division of length.

Then the hold being first sufficiently cleared to admit of the required depths and breadths being properly taken, find the transverse area of the ship at each point of division of the length or each point of division of the parts of the length, as the case may require as follows: Measure the depth at each point of division, from a point at a distance of one-third of the round of the beam below the tonnage deck, or, in the case of a break, below a line stretched in continuation thereof, to the uper side of the floor timber (upper side of the inner plating of the double bottom) at the inside of the limber strake, after deducting the average tickness of the ceiling which is between the bilge planks and the limber strake.

§ 135.175 Finding of transverse area of ship at each point of division of length; manner of taking depths in certain cases.

In the case of a vessel contructed with longitudinal framing, the depths are to be taken to the upper edge or inner surface of the longitudinal frames, where no double bottoms exist. In the case of a ship constructed with a double bottom, the depth shall be taken to the upper side of the inner plating of the double bottom, and that upper side shall, for the purposes of measurement, be deemed to represent the floor timber of the vessel. This rule for measuring the depth of the hold applies to double-bottom ships hav

ing top of double bottom not horizontal. Subject to the provisions of § 135.85 regarding the exemption of double-bottom spaces, if any tank or compartment between the inner and outer plating of the double bottom is used or fitted for the carrying of cargo, the tonnage of the whole of such tank or compartment shall be determined and included in the gross tonnage of the vessel.

§ 135.176 Finding of transverse area of ship at each point of division of length.

If the depth at the midship division of the length does not exceed 16 feet, divide each depth into five equal parts; then measure the inside horizontal breadth at each of the four points of division, and also at the upper point of the depth, extending each measurment to the average thickness in that part of the ceiling which is between the points of measurement. Number these breadths from above (i.e., numbering the upper breadth 1, and so on down to the fifth breadth); multiply the second and fourth by 4, and the third by 2; add these products together, and to the sum add the first breadth and the fifth. Multiply the quantity thus obtained by one-third of the common interval between the breadths, and the product shall be deemed the transverse area of the upper part of the section; then find the area between the fifth and lower point of the depth by dividing the depth between such points into four equal parts, and measure the horizontal breadths at the three points of division and also at the upper and lower points, and proceed as before, and the sum of two parts shall be deemed to be the transverse area; but if the midship depth exceed 16 feet, divide each depth into seven equal parts instead of five, and measure, as before directed, the horizontal breadths at the six points of division, and also at the upper point of the depth; number them from above, as before; multply the second, fourth, and sixth by 4, and the third and fifth by 2; add these products together, and to the sum add the first breadth and the seventh. Multiply the quantity thus obtained by one-third of the common interval between the breadths, and the product shall be deemed to be the transverse area of the upper part of the section; then find the lower part of the area as before directed, and add the two parts together, and the sum shall be deemed to be the transverse area.

§ 135.177 Finding of transverse area of ship at each point of division of length; vessels in which double bottom is horizontal, or in which there is no double bottom.

Sections 135.174-135.178 apply to vessels with double bottoms, the tops of which have a rise from the middle line to each side. In vessels in which the top of the double bottom is horizontal, or in which there is no double bottom, the depths are to be divided by 4 or 6 (instead of 5 or 7), according to whether their midship depths do not or do exceed 16 feet respectively. In such cases no subdivision of the lower part is to be made. § 135.178 Finding of transverse area of ship at each point of division of length; manner of taking depths and breadths in certain cases.

In the case of ships built on the Isherwood system the depths are to be taken to the upper edge of the longitudinal frames, where no double bottom exists. In vessels built of concrete the depths and breadths shall be taken to the inner edge of the main frames. It is to be noted that § 135.177 provides that in vessels without double bottoms no subdivision of the lower part of the transverse area is to be made. On ships built with transverse frames without double bottoms the depths are to be taken to the top of the transverse frames, and no subdivision of the lower section is neces

sary.

§ 135.179 Computation of tonnage.

Number the transverse sections or areas respectively 1, 2, 3, etc., No. 1 being at the extreme limit of the length at the bow, or of each part of the length, and the last number at the extreme limit of the length at the stern or the extreme limit at the after end of each part of the length; then, whether the length be divided according to the table into 4 or 12 parts, as in classes 1 and 5, or any intermediate number, as in classes 2, 3, and 4, multiply the second and every even-numbered area by 4, and the third and every oddnumbered area (except the first and last) by 2; add these products together, and to the sum add the first and last, if they yield anything; multiply the quantity thus obtained by one-third of the common interval between the areas, and the product will be the cubical contents of the space, or cubical contents of each part if the ship is measured in parts

under the tonnage deck. The tonnage of this volume is obtained by dividing it by 100, if the measurements are taken in English feet, and by 2.83 if the measurements are taken in meters. The multiplier 0.353 may be used instead of the divisor 2.83.

§ 135.180 Computation of tonnage between decks above tonnage deck.

If the ship has a third deck the tonnage of the space between it and the tonnage deck shall be ascertained as follows: Measure in feet the inside length of the space at the middle of its height from the plank at the side of the stem to the lining on the timbers at the stern, and divide the length into the same number of equal parts into which the length of the tonnage deck is divided, as above directed; measure (also at the middle of its height) the inside breadth of the space at each of the points of division, also the breadth at the stem and the breadth at the stern; number them successively 1, 2, 3, etc., commencing at the stem; multiply the second and all the other even-numbered breadths by 4, and the third and all the other odd-numbered breadths (except the first and last) by 2; to the sum of these products add the first and last breadths; multiply the whole sum by one-third of the common interval between the breadths, and the result will give in superficial feet the mean horizontal area of the space; measure the mean height of the space, and multiply by it the mean horizontal area, and the product will be the cubical contents of the space; divide this product by 100 (or by 2.83 if the measurements are taken in meters) and the quotient shall be deemed to be the tonnage of the space, and shall be added to the tonnage of the ship ascertained as aforesaid; and if the ship has more than three decks, the tonnage of each space between decks above the tonnage deck shall be severally ascertained in the manner described in this section, and shall be added to the tonnage of the ship ascertained as aforesaid.