Appendix IV — Rules for Tonnage Measurements
The English system of measuring the tonnage of vessels in the eighteenth century is given in Falconer’s Marine Dictionary, 1780, as follows:
“To determine the burden, or, in other words, the tonage, of a ship, it is usual to multiply the length of keel into the extreme breadth of the ship within board, taken along the midship beam, and multiplying the product by the depth in the hold from the plank joining to the keelson upwards to the main-deck, and divide the last product by 94; then will the quotient be the burden required, in tons.”
This rule continued in force till 1819, when it was changed by the Lords Commissioners of the Admiralty as follows:
“Multiply the length of the keel by the breadth of beam, and that product by half the breadth of beam, and divide the last product by 94, and the quotient will be the tonnage” (Marine Dictionary, William Burney, LL.D., 1830). Dr. Burney remarks: “It appears from the general construction of merchant ships, that more attention is paid to evade the tax on tonnage than to their sailing well with the wind in different directions; and if the real tonnage of ships were taken, an alteration would soon be made in the construction for the better.”
This form of the rule continued until 1842, when by Act of Parliament the following method was adopted:
“Divide the length of the upper deck between the after part of the stem and the fore part of the stern-post into six equal parts. Depths: at the foremost, the middle, and the aftermost of these points of division, measure in feet and decimal parts of a foot the depths from the under side of the upper deck to the ceiling at the limber strake. In the case of a break in the upper deck, the depths are to be measured from a line stretched in a continuation of the deck. Breadths: Divide each of those three depths into five equal parts, and measure the inside breadths at the following points—viz., at one fifth and at four fifths from the upper deck of the foremost and aftermost depths, and at two fifths and four fifths from the upper deck of the midship depth. Length: At half the midship depth, measure the length of the vessel from the after part of the stem to the fore part of the stem-post; then, to twice the midship depth add the foremost and the aftermost depths; add together the upper and lower breadths at the foremost division, three times the upper breadth, and the lower breadth, at the midship division and the upper and twice the lower breadth at the after division, for the sum of the breadths; then multiply the sum of the depths by the sum of the breadths, and this product by the length, and divide the final product by three thousand five hundred, which will give the number of tons for register” (Young’s Marine Dictionary, 1846).
In 1854 this rule was changed by the Merchant Shipping Act, which provided that the actual cubic contents of a vessel’s hull should be measured, a registered ton being reckoned as 100 cubic feet. This is known as the Moorsom system, and is still in use and likely to continue. It was adopted by the United States in 1865; Denmark, 1867; Austria, 1871; Germany, France, and Italy, 1873; Spain, 1874; and Sweden, 1875.
The old practice of calculating tonnage in the United States was adapted from the English, and the mode of measurement was as follows:
The length was measured on deck from the fore part of the stem to the after part of the stern-post; the breadth from outside to outside planking at the broadest part of the vessel; the depth of the hold from the plank on deck to the ceiling of the hold. This last measurement was not used, the depth of a vessel for tonnage purposes being assumed to be one half of her breadth. In order to find the tonnage, three fifths of the breadth were deducted from the length and the remainder multiplied by the breadth, and this product multiplied by one half the breadth, or the assumed depth, the last product was then divided by 95, giving the formula:
(L - ⅗ B) × B × ½ B
95
Thus in a vessel measuring 100 ft. x 20 ft. x 18 ft.:
| Length of vessel | 100 |
| Subtract ⅗ breadth | 12 |
| Length for measurement | 88 |
| Multiply by the breadth | 20 |
| 1760 | |
| Multiply by half breadth | 10 |
| 17,600 |
| Divide 17,600 by 95 | and |
| the result is | 185 + 12/19 |
| Total tonnage | 185 + 12/19 |
This mode of measurement continued from colonial times until the Moorsom system was adopted in 1865.
The dimensions of ten representative American and British clippers were as follows:
| Length | Breadth | ||||||
| Nightingale (1851) | 178 | “ | 36 | “ | |||
| American | Oriental (1849) | 183 | ft. | 36 | ft. | ||
| Celestial (1850) | 158 | “ | 34 | “ | 6 in. | ||
| Stag-Hound (1850) | 209 | “ | 39 | “ | |||
| Flying Dutchman (1852) | 187 | “ | 38 | “ | 6 in. | ||
| British | Falcon (1859) | 191 | “ | 4 in. | 32 | “ | 2 in. |
| Taitsing (1865) | 192 | “ | 31 | “ | 5 in. | ||
| Titania (1866) | 200 | “ | 35 | “ | |||
| Spindrift (1867) | 219 | “ | 4 in. | 35 | “ | 6 in. | |
| Thermopylæ (1868) | 210 | “ | 36 | “ | |||
Although these British ships show less breadth than the American, yet they have more breadth in proportion to length than the earlier British clippers, such as the Stornoway (1850), Lord of the Isles (1855), etc.
Footnotes
1 A frigate was a ship designed to be a fast, armed cruiser and mounted from twenty to fifty guns; when a naval vessel mounted less than twenty guns she became a sloop of war, and when she mounted more than fifty guns she became a line-of-battle ship. The frigate was always a favorite type of vessel with the officers and men of the navy, as she was faster and more easily handled than a line-of-battle ship, and was at the same time a more powerful fighting and cruising vessel than a sloop of war. Frigate-built means having the substantial construction, arrangement of the decks, masts, spars, rigging, and guns of a frigate.
2 When peace was declared in 1783, the Government of the United States sold or otherwise disposed of all its vessels, a fact that was quickly taken advantage of by the Barbary corsairs. They at once began to prey upon American merchant shipping in the Mediterranean and even in the Atlantic, and made slaves of the captured crews. The French and English, too, in their wars with each other, by no means respected the neutrality of American commerce, the former being the worse offenders. It was not, however, until 1794 that Congress again authorized the formation of a navy, under the Secretary of War, and in 1798 the office of Secretary of the Navy was created. Among the vessels built in 1794-98 was the frigate Constitution, the famous “Old Ironsides” which still survives. The separate States had meanwhile maintained vessels for the protection of their own coasts, and, of course, there had been no cessation in the building of merchant ships during the period preceding the War of 1812.
3 A typean was the head merchant of one of the Company’s “factories” or mercantile houses, such as were later known in China as “hongs.”
4 Annus Mirabilis, stanza 89 (1667).
5 Second American edition, translated by H. Reeve, pp. 403-4.
6 New York Commercial, October 8, 1851.
7 William John, in an article on clipper ships in Naval Science, vol. ii. (1873), p. 265.
8 The various systems of calculating the tonnage of vessels which were in force in Great Britain prior to 1854, (see Appendix iv.,) gave the breadth measurement a preponderating influence upon the result, and as taxation, port, and light dues, etc., were based upon the registered tonnage of a vessel, there was economy in decreasing the breadth of a vessel at the expense of the other dimensions. Ship-builders and owners in England showed a much greater tendency to profit by this feature of the law than did those in the United States, where substantially the same system was in force. In this country some very narrow vessels were built for the New Orleans and West India trade, in the period 1820-1845, but it was found that the saving in taxation did not pay for using such an undesirable type of vessels, so they were given up. As a rule, American owners and builders preferred to build vessels of a type which they regarded as the best for speed and for the trade in which they were engaged, without regard for the tonnage laws.
9 The Challenge.
10 Forbes’s rig was invented by Captain R. B. Forbes, and was first put on the topsail schooner Midas in 1841, afterwards on the auxiliaries Edith, Massachusetts, and Meteor; ships, R. B. Forbes, Lintin, Flying Childers, Aurora, Cornelius Grinnell, and probably others. In this rig the topmast was fidded abaft the lowermast head, and the lower topsail yard hoisted on the lowermast head from the eyes of the lower rigging to the cap. The lower topsail had two reefs with reef-tackles, buntlines, and clew-lines, as in the single topsail rig. The upper topsail hoisted on the topmast and had the same gear as the lower topsail. Sometimes the topmast was fidded before the lower masthead, and then the lower topsail yard hoisted on the doubling of the topmast. This rig was an improvement upon the single topsail rig, but was eventually superseded by Howes’s rig, which was invented by Captain Frederic Howes, of Brewster, Massachusetts, who in 1853 first put it on the ship Climax, of Boston, which he commanded. Captain Howes took out a United States patent for his rig in 1854. In this rig, the lower topsail yard is slung by a truss at the lower mast cap; indeed, Howes’s rig is the double topsail rig of the present day, though one does not often hear the name of Captain Howes in connection with it.
11 Mr. Everett is reported to have said “eighty-two,” but if he did so, it was a mistake, for forty-two is the true number.
12 These slabs were subsequently removed, one side being washed away.
13 The following are some of these house flags: The crimson field and black ball, of Charles H. Marshall; the red, white, and blue swallowtail, of Grinnell, Minturn & Co.; the yellow, red, and yellow horizontal bars with white “L” in centre, of A. A. Low & Brother; the thirteen blue and twelve white squares, of N. L. & G. Griswold; the crimson field and yellow beehive, of Sutton & Co.; the crimson field, white border, and white “D” in centre, of George Daniels; the red, white, and red vertical stripes with red “B” in centre, of Vernon H. Brown; the blue and white half-diamonds, of Russell & Co.; the crimson field and white diamond, of Augustine Heard & Co.; the white above blue and red ball in the centre, of Sampson & Tappan; the white above yellow and red star in centre, of Glidden & Williams; the narrow blue and white horizontal stripes with red ball in the centre, of Napier, Johnson & Co.; the white field and blue cross, of George B. Upton; the crimson swallowtail and blue cross, of Charles R. Green; the white swallowtail, red cross with white diamond in the centre, of R. W. Cameron; the crimson swallowtail, blue cross, and white ball in the centre, of Wells & Emanuel; the blue above white, white ball in blue and red ball in white, of D. & A. Kingsland; the white field and red cross in the centre of D. G. & W. B. Bacon; the white swallowtail and black S. & B., of Snow & Burgess; the white field and black horse, of William F. Weld & Co. The flag of Howland & Aspinwall had a blue square in the upper corner of the luff and lower corner of the fly; the rest of the flag was white with narrow blue lines in the lower corner of the luff and upper corner of the fly, which formed squares, and also formed a white cross extending the full hoist and length of the flag. David Ogden’s flag was a white field and red cross; Crocker & Warren’s, blue above yellow with a yellow “C” in the blue and blue “W” in the yellow. Then there was the red swallowtail with white cross and black star in the centre, of Samuel Thompson & Nephew; the blue field, white diamond, and black star, of Williams & Guion; the crimson field and black “X” of John Griswold. These were the private signals of most of the leading New York and Boston ship-owners, which, half a century ago, enlivened the water front of New York, though there were some others which have now faded from memory.
14 Walter Savage Landor.
15 Democracy in America (1835); Second American edition, p. 408.
16 See Appendix IV.
17 A lorcher is a fast Chinese vessel, used a good deal by fishermen, and in former times by the Chinese pirates and smugglers.
18 The Thermopylæ repeated this remarkable passage of sixty-three days from London to Melbourne during the following year.