380 Ships built on Isher- wood system. If ship has a third deck. Permanently eov- ered, etc., space on or above upper deck. PROCLAMATIONS, 1937 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 their midship depths do not or do exceed 16 feet respectively. In such cases no subdivision of the lower part is to be made. 30. 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 section 2, paragraph 29, 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 necessary. 31. SEC. 3 . 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 ac- cording 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 odd- numbered area (except the first and last) by 2; add these products together, and to the sum add the first and last, if they yield any- thing; 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. 32. SEC. 4 . 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 tim- bers 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 above described, and shall be added to the tonnage of the ship ascertained as aforesaid. 33. SEC. 5 . If there be a break, a poop, or any other permanently covered or closed-in space on or above the upper deck (as defined above
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