Register Tonnage and its Measurement, Page 231 
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REGISTER TONNAGE AND MEASUREMENT 231 practical in service, and moreover by encouraging light scantlings, especially in wooden hulls, would have undone the work of Lloyd's Register and the other classification societies. Parliament therefore declined to adopt the report, and included instead in the great Merchant Shipping Act17 of 1854 a measurement system worked out by the naval architect George Moorsom, who had been secretary to the 1849 commission. The Moorsom System remains to this day the foundation of the tonnage registry laws and measurement rules of the maritime nations of the world, as well as of the Suez and Panama Canals. The basis of this system is the use of the Simpson or parabolic rule to calculate the transverse areas of the interior of the ship below the tonnage deck (defined as the second deck from below in vessels with three or more decks to the hull; otherwise the upper deck) at an odd number of equidis· tant sections, by means of widths measured at an odd number of equidistant depths at each section. The same rule is then used to compute the interior volume from the areas.18 The volumes of enclosures above the tonnage deck are determined separately and the sum of all the volumes is finally divided by 100 to obtain the tonnage; that is, 100 cubic feet (2.83 cubic meters) equals a register ton. The choice of this divisor followed the precedent established with the 'new measurement' of 1836, the number being chosen 'in order to bring out ... as nearly as may be the aggregate of the nominal tonnage of former laws, so that the statistical tonnage of the kingdom should remain unaltered, as well as all revenues which, from early times, may have been founded on that standard.' 19 By carefully measuring a selected series of vessels, Moorsom deduced that there was 363,412,456 cubic feet in the ships ofthe British merchant marine, which totalled 3,700,000 register tons; 20 hence a ton was 98.2 2 cubic feet or for convenience, 100. As an alternate rule for vessels encumbered with bulkheads or cargo, Moorsom measured the girth from the upper deck at each side at the widest part of the vessel, the breadth outside at the widest part, and the length on the upper deck from the rabbet of the stem to the rabbet of the 17 17 and 18 Viet., c. 104, sec. 2029. 18 The area of a curvilinear space is found by 'dividing the base into a suitable even number of equal parts, erecting perpendicular ordinates from the base to the curve, and after measuring off the lengths of these ordinates, to the sum of the end ones add four times the odd and twice the even ordinates. The total sum multiplied by onethird the common interval between these ordinates, will produce the area.' G. Simpson, The Naval Constructor (4th ed., New York, 1918), pp. 12. The areas at each section having been found, they are treated as ordinates in the same way, and integrated along the length to yield the volume. The formula is exact when used with a parabola (or rectangle); with other curves its accuracy increases with the number of measurements taken. 19 Reed, quoting Moorsom, in Naval Science, I (1872), 393. 20 Johnson, p. 45.
Object Description
Title  Volume V. No. 3 July 1945 
Description  Articles include: 'The Fleet' by Sidney G. Morse; Voyage of the Brig Nabob from Boston to Batavia, Java, in 1833 From a letter by Captain George W. Putnam, of Salem, to his sisters Edited by Ralph Newell Thompson; The Dismal Swamp Canal by Alexander Crosby Brown; Register Tonnage and its Measurement by John Lyman; and Mutton Spankers and Ringtail Topsails by Captain P. A. McDonald. Documents, News, and Book Reviews are also included. 
Date  1945, July 
Subjects  Amphibious warfare; Brigantines; Brown, Alexander Crosby, 1905; Canals; Dismal Swamp Canal (N.C. and Va.)—History; Dugout canoes; Lake Drummond (Va.); Letter writing; Letters; Lyman, John, Dr., 19151977; Marine canvas work; Masts and rigging; McDonald, P. A., Captain; Morse, Sidney G. (Sidney Gilbert), 19031982 ; Naval architecture; Naval history; Privateering; Putnam, George W.; Sailing ships; Seafaring life; Ships – Measurement; Thompson, Ralph Newell; Tilden, Bryant P. (Bryant Parrot), 17811851; Tonnage – Measurement – Law and legislation; United States. Continental Navy; United States. Navy – History; United StatesHistoryRevolution, 17751783Naval operations; Voyages and travels; Washington, George, 17321799 
Publisher  Peabody Essex Museum, Salem, Massachusetts 
Sponsor  This digitization project was sponsored by the Salem Marine Society. 
Format  A Quarterly Journal of Maritime History and Arts 
Publication Rights  Requests for permission to publish material from this collection must be submitted in writing to The Russell W. Knight Curator of Maritime Art and History at the Peabody Essex Museum. 
Description
Title  Register Tonnage and its Measurement, Page 231 
Author  John Lyman 
Description  REGISTER TONNAGE AND MEASUREMENT 231 practical in service, and moreover by encouraging light scantlings, especially in wooden hulls, would have undone the work of Lloyd's Register and the other classification societies. Parliament therefore declined to adopt the report, and included instead in the great Merchant Shipping Act17 of 1854 a measurement system worked out by the naval architect George Moorsom, who had been secretary to the 1849 commission. The Moorsom System remains to this day the foundation of the tonnage registry laws and measurement rules of the maritime nations of the world, as well as of the Suez and Panama Canals. The basis of this system is the use of the Simpson or parabolic rule to calculate the transverse areas of the interior of the ship below the tonnage deck (defined as the second deck from below in vessels with three or more decks to the hull; otherwise the upper deck) at an odd number of equidis· tant sections, by means of widths measured at an odd number of equidistant depths at each section. The same rule is then used to compute the interior volume from the areas.18 The volumes of enclosures above the tonnage deck are determined separately and the sum of all the volumes is finally divided by 100 to obtain the tonnage; that is, 100 cubic feet (2.83 cubic meters) equals a register ton. The choice of this divisor followed the precedent established with the 'new measurement' of 1836, the number being chosen 'in order to bring out ... as nearly as may be the aggregate of the nominal tonnage of former laws, so that the statistical tonnage of the kingdom should remain unaltered, as well as all revenues which, from early times, may have been founded on that standard.' 19 By carefully measuring a selected series of vessels, Moorsom deduced that there was 363,412,456 cubic feet in the ships ofthe British merchant marine, which totalled 3,700,000 register tons; 20 hence a ton was 98.2 2 cubic feet or for convenience, 100. As an alternate rule for vessels encumbered with bulkheads or cargo, Moorsom measured the girth from the upper deck at each side at the widest part of the vessel, the breadth outside at the widest part, and the length on the upper deck from the rabbet of the stem to the rabbet of the 17 17 and 18 Viet., c. 104, sec. 2029. 18 The area of a curvilinear space is found by 'dividing the base into a suitable even number of equal parts, erecting perpendicular ordinates from the base to the curve, and after measuring off the lengths of these ordinates, to the sum of the end ones add four times the odd and twice the even ordinates. The total sum multiplied by onethird the common interval between these ordinates, will produce the area.' G. Simpson, The Naval Constructor (4th ed., New York, 1918), pp. 12. The areas at each section having been found, they are treated as ordinates in the same way, and integrated along the length to yield the volume. The formula is exact when used with a parabola (or rectangle); with other curves its accuracy increases with the number of measurements taken. 19 Reed, quoting Moorsom, in Naval Science, I (1872), 393. 20 Johnson, p. 45. 
Date  1945, July 