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522 to a great deal of dissatisfaction, and was never popular. A third committee was appointed in 1849, and they recommended that ton- nage should depend upon the entire cubic content of a vessel measured ex- ternally and including poop, forecastle Yand other covered-in spaces. Transverse sections were to be measured, and a curve constructed in which the ordi- nates represented to scale the area of each section, and the cubic content was found by calculating the area of this curve. The result was to be divided ' by 35,.and then--multiplied by 0.27, a factor chosen to give a result equal to the average result of the old law. A bill was introduced into parliament in 1850 to give effect to these recom- mendations, but met with so little favor that it was withdrawn. Basis of Present Laws Mr. Moorsom then proposed, in the latter part of 1850, a scheme for the calculation of tonnage based upon in- ternal measurement, so as to obtain the correct internal capacity of vessels, a register ton being 100 cubic feet of internal measurement. The divisor 100 was fixed upon, both for its convenience and to give a result practically corre- sponding with that under the old law. This scheme is embodied in the mer- chant shipping act of 1854, which with some modifications in details is the ex- isting law for tonnage measurement, and the rules laid down in the act of 1854 may be briefly stated as follows: The tonnage deck is the upper deck in vessels with less than three decks, and the second deck from below in all other ships. The length is measured in a straight line along the upper side of the ton- nage deck from inside of inside plank (average thickness) at the side of stem to the inside of the midship stern tim- ber or plankther, as the case may be~- (average thickness), deducting what is due to the rake of the stern' timber in the thickness of the deck and in one- third of the round beam, and the length so obtained is divided into a number of equal parts according to the follow- ing table: Divide into Length, feet equal parts RO Oe toe ee cls cas 4 Above 50 not exceeding 120............ 6 Above 120 not exceeding 180............ 8 Above 180 not exceeding 225............ 10 BOVE COG ee ec lek os tins c cess ese 12 At these points in the vessel's length a transverse vertical section of the in- ternal volume is then measured by the following method: The depth at each point of division is measured from a point one-third the round of beam below the deck, or, in the case of a break, from a line THE MARINE REVIEW stretched in continuation thereof to the upper side of the ceiling, and if the depth as taken at the midship division does not exceed 16 feet, each depth is divided into four equal parts, and the horizontal breadths measured at each of the points of division, and also at the upper and lower points of the depth, the breadth being taken to the inside of ceiling, allowing an average thickness. By the application of Simp- son's first rule, the area of each trans- verse section is then found by multi- plying the second and fourth breadth by 4, and the third by 2; these prod- ucts added together to the first and fifth breadths, and the sum multiplied by one-third the common interval, give the area. If the midship depth exceeds Upper Deck Light and A/T Space L£rgine Foon FIG. 2--MEASURING ENGINE ROOM LIGHT AND AIR SPACES 16 feet, each depth is divided into six equal parts, the second, fourth and sixth breadths -are multiplied by 4, the third and fifth by 2 and these prod- ucts added to the first and seventh breadths, and this multiplied by one- third the common interval, give the area. Having obtained the area of each transverse section, the register tonnage is computed as follows: Member the aféas, 1, .2, 3, etc. No. 1 being at the extreme limit at the bow and the. last number the extreme limit at the stern; then multiply the second and every even-numbered area by 4, and the third and every odd-numbered area, excepting the first and the last, by 2, add these products together and to the sum add the first and last if they yield anything; multiply the quan- tity thus obtained by one-third the common interval between the areas, and the product will be the cubical con- tents of the space under the tonnage deck; divide this product by 100, and the quotient will be the tonnage under the tonnage deck. Fig. 1 illustrates the manner in which the length and depth of the vessel are divided for measurement. In vessels fitted: with partial double bottoms for water ballast .and also in cases where the inner bottom is not horizontal, but sloping upward toward the side, additional subdivisions and September, 1920 measurements are made in order" to calculate the internal capacity of the vessel. Peak tanks, constructed for carrying water ballast only, and not available for cargo or stores, are, under certain conditions, allowed to be deducted from the gross tonnage. Having ascertained the tonnage un- der the tonnage deck, there are various additions to be made to obtain the gross register tonnage, and deductions to be made from the gross to give the net register tonnage, upon which dues and charges are based. The act provides that if there be a break or poop or any permanent en- closed-in space on the upper deck ayail- able for cargo or stores or for the berthing or accommodation of passen-_ gers or crew, the tonnage shall be ascertained thus: Measure the internal mean length of such spaces in feet and divide it into equal parts; measure at the middle of its height three inside breadths--namely, one at each end, and the other at the middle of the length, then to the sum of the end breadth add four times the middle breadth and multiply the sum by one-third the common interval between the breadths; the product will give the mean _hori- zontal area of such space; multiply this product by the mean height, and divide by 100, and the quotient will be the tonnage which is to be added to the under deck tonnage, subject to the following provision, that nothing shall be added in respect cf any _ building erected for the shelter of deck passen- gers, and approved by the board of trade, Rules for Extra Decks Ifthe ship has a third deck; thé space between it and the tonnage deck is found by dividing the length into the same number of intervals as used in computing the tonnage under the tonnage deck, and having found the mean horizontal area of the space by the rule already given, this mean area multiplied by the mean height and divided by 100 gives the tonnage of the 'tween deck space, to be added to the tonnage already found for the por- tion below the tonnage deck; and if the vessel has more than three decks, the tonnage of each space between decks above the tonnage deck is similarly - calculated. Hatchways over cargo holds are also measured, and any excess above 0.5 per cent of the remaining gross tonnage is added to the gross tonnage. The merchant shipping act of 1854 also gives a rule for ascertaining ap- proximately the tonnage of a_ vessel "measured for 'any purpose other than registry," and having cargo on board;