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RULES CONCERNING SUPERSTRUCTURES AND “SHELTER” DECKS: HISTORY AND
The provisions of the several measurement rules now in force differ largely as regards the exemption, measurement, and deduction of spaces within superstructures above the uppermost full-length deck. The same is true of the spaces between the upper and so-called "shelter" deck. The treatment accorded superstructures and especially the 'tween deck, “shelter” deck spaces may largely affect the gross and net tonnage of a vessel. It is as necessary that the rules regarding the exclusion or inclusion of spaces above the upper deck should be specific and exact as that a correct rule should be followed in making deductions for propelling power. Indeed, it was made clear by the facts presented in Chapters IV and V that greater inaccuracy in tonnage may, in the case of a vessel having what the British and German rules consider to be a shelter deck, result from exempting from measurement the entire space between the upper and "shelter” deck than from applying the 32 per cent rule to the deductions made for spaces occupied by propelling power.
The term " superstructure” as used in this chapter, refers to all erections on or above the uppermost full-length deck—such as poop, forecastle, bridge houses, round houses, and side houses. By “shelter” deck spaces are meant those under an uppermost full-length deck provided with such tonnage openings as will cause the space between the "shelter” and upper decks to be exempted from measurement by the British and German rules. In the several measurement rules, the spaces under an uppermost deck with tonnage openings are sometimes spoken of as "shelter” deck spaces and sometimes as awning deck spaces. The dissimilarity in the provisions of the measurement rules as regards the inclusion or exclusion of superstructure and "shelter” deck spaces is due mainly to the different definitions given to “uppermost closed-in” deck and "open" spaces. The measurement rules of the United States, Great Britain, and Germany stipulate that spaces permanently closed-in and"available for cargo or stores or for the berthing or accommodation of passengers or crew" shall be measured, and that spaces which are open or not available for cargo or stores or for the berthing or accommodation of passengers or crew shall be exempted from measurement. The phraseology of the three measurement codes as regards the treatment to be accorded “shelter" deck spaces and the first tier of superstructures above the uppermost full-length deck is practically identical, but the rules are interpreted differently in Great Britain and Germany than in the United States, with the result that the same vessel would be accorded different gross and net tonnages by the American rules. The tonnage rules of the Suez Canal Co., like those of Great Britain, Germany, and the United States, exempt from measurement open superstructures and include in measurement and tonnage “permanently covered and closed-in spaces on the upper deck”; but the Suez rules differ in numerous details from the national rules as to the treatment of superstructures. In a word, there is great lack of uniformity among the several measurement codes as to the exclusion from tonnage, and as to the inclusion therein and deduction therefrom of spaces above the upper
deck. The rules recommended for the measurement of vessels to determine the tonnage upon which the Panama Canal tolls shall be levied adhere strictly to the principle that the gross tonnage of a vessel shall include its entire closed-in capacity. Only spaces which are actually open and not available for passengers or cargo are exempted from measurement and only such measured spaces are deducted from gross tonnage to determine net tonnage as are required for the operation and navigation of the vessel. The spaces to be deducted from gross tonnage are enumerated in the rules and the deductions from gross tonnage are to be only the enumerated spaces.
In carrying out these principles, the Panama measurement rules differ from those of Great Britain, Germany, the United States, and the Suez Canal Co. as regards the measurement and deduction of spaces in superstructures. The spaces between the “shelter” deck and the upper deck are treated as are all other spaces, that is, if they are closed-in they are included in gross tonnage and if available for cargo or passengers they are included in net tonnage. The reasons for the variation of the Panama rules from the more important measurement rules now in force will be made clear, and it is believed the force of the reasons will also be made apparent, by a brief presentation of the history of the treatment accorded spaces under “shelter" decks and within superstructures by the measurement rules of Great Britain, the Suez Canal Co., Germany, and the United States. The historical background thus given to the rules recommended for Panama will, it is believed, show that the proposed rules are based upon correct principles and represent an advance over the tonnage rules now in effect. HISTORY OF THE TREATMENT OF SPACES IN SUPERSTRUCTURES AND UNDER “SHELTER" DECKS
IN THE MEASUREMENT RULES OF GREAT BRITAIN. The first British statute that included within gross tonnage' any spaces above the upper deck was the act of 1835, which provided for the measurement of “a poop or half deck or a
1 Rules for the measurement of vessels first appeared in laws imposing customs duties upon articles of commerce. One of the earliest imports taxed was wine from the Continent, which was imported in tuns. The dues imposed by Parliament upon each tun of wine led to the use of the word tunnage as an expression of the capacity of the open or partial-decked boats used in transporting the casks of wine. By the act of Parliament of 1423 a tun of wine was to measure not less than 252 gallons, old English measurement; and, although the gallon was not an exact unit, a tun of wine weighed approximately 2,240 pounds and the tunnage of one of these wine vessels would be practically equivalent to its deadweight capacity or tonnage. Other commodities than wine were charged dues based upon weight or "poundage."
Another article of commerce that was early taxed was coal. The act of Parliament of 1422 imposed a duty of 2 pence per caldron upon coals carried in the “keels” employed at Newcastle-on-Tyne. The caldron contained about 53 hundredweight of coal and a standard load for the “ keels then used at Newcastle was 10 caldrons, or 264 tons. In 1679, the duty that had been imposed upon “keels” at Newcastle was placed upon vessels employed upon the Wear.
In 1694, Parliament changed the duty upon coal to a tax upon the deadweight of the coal instead of upon each caldron of coal. The coal barges or boats when empty were loaded with actual weights of iron or lead until the maximum load of 264 tons had been placed in the boat. Then the load-water line was marked upon the boat by nails driven in the hull at the stem, at the stern, and at each side amidships. By an act of 1775, this law which had previously applied to coal carried on the Tyne and on the Wear was applied to vessels loading coal in all parts of the United Kingdom. The act applied to coal and only to boats used within the country; it did not apply to sea-going ships.
The first customs act of Parliament that required sea-going and coasting ships generally to be measured was enacted in 1694. This act imposed duties upon the tonnage of vessels and the tonnage was to be determined by multiplying the length of the keel by the breadth of the vessel amidships and by multiplying this product by the depth of the hold below the upper deck. The duties imposed by the act of 1694 were repealed in 1696. An act passed that year provided for the registry of shipping, but no rules for the measurement of vessels were contained in the act which, as far as tonnage was concerned, simply required the owners of vessels to declare upon oath the tons burden of the vessel's registry.
From 1696 until 1773 there was no general rule for the measurement of vessels applied to shipping generally. In 1720, an act was passed prohibiting the importation of spirits in vessels of less than “30 tons burden and under" and "for the preventing of disputes that may arise concerning the admeasurement of ships laden with brandy and other spirits.” The law contained the following rule to be applied to the measurement of such vessels as it was necessary to measure in order to enforce the act of 1720: "Take the length of the keel within board (so much as she treads on the ground) and the breadth within board by the midship beam, from plank to plank, and half the breadth for the depth, then multiply the length by the breadth, and that product by the depth, and divide the whole by 94; the quotient will give the true contents of the tonnage.”
In 1773 the formula of 1720, by which only a comparatively few vessels employed in one kind of trade had been measured, was applied in a modified form to all merchant vessels. The tonnage resulting from the application of the act of 1773 is spoken of as “British Old Measurement" (B. O. M.) tonnage. The measurement formula was as follows:
Tonnage B. O.M. L in the formula is the length of the vessel along the rabbet of the keel from the back of the main stern post to a perpendicular line on the fore part of the main stem under the bowsprit. B in the formula is the breadth from the outside of the planking at the broadest part of the ship.
It will be noted that the act of 1773 substituted one-half the breadth for the depth in the factors to be multiplied together to determine the contents of a vessel. At that time the breadth was approximately twice the depth and the formula was fairly accurate. This feature of the tonnage formula of 1773, however, soon caused vessels to be built with depth disproportionate to their breadth and length and the law had a bad influence upon ship designs. In 1786 the B. O. M. tonnage formula was changed by requiring the length of the vessel to be taken not along the keel but along the load-water line, and the length of the vessel for tonnage measurement was taken from the back of the stern post to the front of the main stem with a deduction therefrom of 3 inches for each foot of the load-water draft. This deduction was to account for the rake of the stern abaft.
The only other important change made prior to 1835 in the act of 1773 was contained in the law of 1819, which provided that in measuring steam vessels the length of the engine room should be deducted from the vessel's length in calculating tonnage. This provision led to the abuse of constructing the engine-room in two parts, one well forward and the other aft, with an intervening space between the two parts of the engine-room. The distance between the forward bulkhead and the after bulkhead of the engine room thus was made to include the greater part of the length of the vessel.
The abuses that developed under the act of 1773 led to the appointment by the Admiralty of a committee to investigate the subject of tonnage in 1821. The report made by this committee was not acted upon and another committee was appointed by the Admiralty in 1833. The report of this committee led to the enactment of the law of 1835—the “new measurement" law--which provided for a much more accurate system of measurement than had previously prevailed. The depth of empty vessels was taken at three points and the breadth also at three points, and a complicated scheme of breadth and depth factors was included in the tonnage formula. The tonnage of loaded vessels was ascertained by dividing the product of the length, breadth, and depth by 130. The tonnage of the spaces in poops and under decks raised above the upper deck was ascertained by dividing the product of the mean inside length, breadth, and depth by 92.4. The tonnage allowance for engine-room space was the product of the length of the engine room between the forward and aft bulkheads, of the depth of the vessel amidships and of the breadth of the ship amidships at two-fifths the depth from the deck divided by 92.4. This "new measurement” rule remained in force until it was superseded by the Merchant Shipping Act of 1854.
For the history of British tonnage rules consult Report of Royal Commission on Tonnage, 1881, Appendixes 1 to 9, for the statutes; Lloyd's Calendar, 1911, pp. 277 et seq.; White, W. H., Manual of Naval Architecture, 5th edition, 1900, Chapter II; Holms, Sir George C. V., Ancient and Modern Ships, Part II, Appendix 2, 1906; Tho Nautical Gazette, Vol. LVIII (1889), pp. 1, 89, and 173.
break in the upper deck," and for the inclusion of the spaces thus measured in the gross tonnage. The formula by which tonnage was determined under the act of 1835—the so-called “New Measurement" law—was to multiply together the mean length, breadth, and height of measured spaces and to divide the product by 92.4.
The “New Measurement" law of 1835 proved unsatisfactory because the tonnage formula was inaccurate; and, also, because the law was so worded that excessive deductions were made for propelling power. Nor did the law take into account all superstructures. The dissatisfaction with the act of 1835 led to the appointment by the Admiralty of a tonnage commission in 1850, which, as has been explained, was in favor of a less desirable system of measurement than had been established by the act of 1835. The commission recommended a system of external measurement of vessels to determine their tonnage. This report having failed to receive the sanction of Parliament, Mr. George Moorsom worked out an accurate method of determining the cubical contents of spaces within vessels and the “Moorsom system” was incorporated in the act of 1854.
The act of 1854, which adopted Mr. Moorsom's system of measurement and stipulated that 100 cubic feet should constitute a ton, provided for the measurement of superstructures as follows:
If there is a break, a poop, or any other permanent closed-in space on the upper deck available for cargo or stores, or for the berthing or accommodation of passengers or crew, the tonnage of such space shall be ascertained * and shall be added to its tonnage under the tonnage deck, ascertained as aforesaid, subject to the following provisos: First, that nothing shall be added for berthing of the crew unless such space exceeds one-twentieth of the remaining tonnage of the ship, and in case of such excess the excess only shall be added; and, secondly, that nothing shall be added in respect of any building erected for the shelter of deck passengers and approved by the Board of Trade.
The foregoing provisions of the act of 1854, and also one other section of the act, have led to controversy and to serious administrative difficulties in applying the acts of 1854 to the space between the upper deck and the one above it, usually called the "shelter” deck. The act of 1854 stipulates that,
If the ship has a third deck, commonly called a spar deck, the tonnage of the space between it and the tonnage deck shall be ascertained * * and shall be added to the other 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 manner above described and shall be added to the tonnage of the ship, ascertained as aforesaid.
If the space between the upper deck and the deck above it were permanently closed-in, it would be measured and included in gross tonnage under the provisions of the act of 1854. If, however, the space was really or, as it has turned out, technically not permanently inclosed, the space was exempted from measurement. The problems connected with the measurement, exemption, and deduction of spaces in superstructures above the uppermost deck and of spaces between the upper and “shelter” deck are different and may best be treated separately. It will be well to present first the history of the controversy regarding "shelter” deck spaces.
The Merchant Shipping Act of 1854 makes no reference to a “shelter” deck, but refers to a spar deck above the upper deck. A spar-decked ship, and also the awning-decked ship, had a definite meaning at the time of the passage of the act of 1854. They were three-decked ships having lighter scantlings and plating above than below the second deck. The space between the main deck and the awning deck, or the spar deck, was completely closed-in and was, without question, included in the gross tonnage under the act of 1854.
At various times during the 1860's, however, shipowners applied to the Board of Trade for the exemption of spaces between the upper and spar or awning decks, and during the 1870's strong pressure was exerted by shipowners to secure the exemption of 'tween-deck spaces under the awning deck. The term "awning deck" seems to have arisen in connection with the carriage of passengers in the East Indian trade and cattle in the North Atlantic trade. The spaces under the awning deck were not permanently closed-in and were entitled to exemption from measurement and gross tonnage, but gradually the space between the upper and awning deck was subdivided by numerous cross bulkheads and the sides and deck were so constructed as to make the 'tween-deck space under the awning deck practically closed against the sea. It