For single-decked Vessels. The tonnage is found by multiplying the extreme length by the extreme breadth, and the product by the extreme depth, and divided by 94 as above. NETHERLANDS. The length is measured on deck from the stem to the sternpost. For the breadth, the hold is divided into four portions, and two measurements taken at each of the three divisions: 1. Across the keelson, on a level with its upper surface, from ceiling to ceiling. 2. The greatest breadth of the hold at each division. The mean of these six measurements is considered the breadth. The depths are taken at each of the foregoing points of division from the upper surface of the keelson to the lower surface of the upper deck between the beams, and the mean of these three is assumed. The length, breadth, and depth, are then multiplied together, and two-thirds of the product is considered as the tonnage. But an allowance for provisions and water, cabins and ship's stores, varying from 3 to 456, is deducted from the depth before it is multiplied by the length and breadth. NORWAY. From the after part of the stem the length of the ship is taken to the inner part of the stern-post. Dividing the length of the vessel into four equal parts, the breadth is measured at each of those divisions. The depth of the vessel from the under surface of the upper deck to the keelson to be taken at the above three points of division. Then multiply the length by the mean of the three breadths, and the product thereof by the mean of the three depths. The result of the foregoing is divided by 2424, if there be no fractional parts of feet; but if there are, the calculation is made in inches, and the divisor becomes 322767, the result thus obtained being the burthen of the vessel in wood lasts, of 4000 Neva pounds each. To reduce these into commerce lasts, one of which is equal to 5200 Neva pounds, it is multiplied by 10, and divided by 13. RUSSIA. Length of the keel in feet multiplied by the extreme breadth over the sheathing, and the product multiplied again by half the breadth, and divided by 94, gives the number of English tons. UNITED STATES. If the vessel be double-decked, the length is taken from the fore-part of the main stem to the after part of the stern-post above the upper deck. The breadth, at the broadest part above the main-wales, half of which breadth is accounted the depth. From the length three-fifths of the breadth is deducted; the remainder is multiplied by the breadth, and the product by the depth. This last product is divided by 95, and the quotient is deemed the true contents or tonnage of such ship or vessel. If the ship or vessel be single-decked, the length and breadth are taken as above for a double-decked vessel; and three-fifths of the breadth is deducted from the length. The depth of the hold is taken from the under side of the deck-plank to the ceiling in the hold; these are multiplied and divided as aforesaid, and the quotient is the tonnage. At Philadelphia, a system of measuring, called carpenter's tonnage, appears to be adopted. The rule is as follows: For Vessels with one Deck. Multiply the length by the breadth of the main beam, and the product by the depth. Divide this second product by 95. For double-decked Vessels. Take half the breadth of the main beam for the depth, and work as for a single-decked vessel. At New Orleans the mode at present in use is as follows: Take the length from the stem to the after-part of the stern-post on the deck. Take the greatest breadth over the main hatch, and the depth from the ceiling of the hold to the lower surface of the deck at the main hatch. From the length deduct ths of the breadth, multiply the remainder by the actual breadth and depth, and divide by 95, for a vessel with a single deck; but if the vessel have a double, half the breadth of the beam is considered as equivalent to the depth, and is multiplied accordingly. PROPOSED BY THE COMMITTEE APPOINTED BY THE ADMIRALTY IN 1821. 1. Measure the length in feet and inches from the after part of the stem to the fore part of the stern-post; on the level of the deck, or of the upper deck, when there are more than one. 2. Divide the length into four equal parts, and measure the depth, at each point of division; from the under surface of the upper deck plank to the upper surface of the ceiling, near the keelson, or the limber-strake. 3. Divide the middle depth into two equal parts, and measure 4. Divide each of the other two depths into four parts, and measure the breadth at the two quarters of each; that is, at a Rule for the Computation.-Add together the five breadths, and multiply the sum by the half sum of the two depths at the quarter lengths, and by the length; the product, divided by 560, will give LET the following lines be measured, and each of them marked at the extremes by government nails* being driven into the plank or 1st. The extreme length on the upper deck, no notice being taken of a poop deck or raised forecastle. 2nd. The inside breadth on the upper deck, at the middle of the 3rd. The depth from the under part of the upper deck to the 4th. The inside main breadth, at the widest part in the line of 5th. The inside length, at a height from the ceiling equal to 6th. The inside breadth, at a height equal to one-fourth of the main breadth for the ceiling, and in the perpendicular line, at a 7th. The inside breadth, at the same height, and at one-sixth the length from aft, the length alluded to in both being that of the For the Contents of the Upper Division.-From the mean of the two lengths, take one-tenth part for the round of the side; multiply the remainder by the mean of the upper breadth and main breadth, and again by the difference between half the main For the Contents of the Lower Division.-From the length at the height equal to half the main breadth, take three-fifths of the inside main breadth for the rake of the stem and stern-post, and one-fifth of the remainder for the round of the bottom, then multi- ply by the inside main breadth, and again by half that breadth; the result will give the cubic contents, in the generality of well- Some vessels, however, are built uncommonly full, and a few sharp, like men-of-war; it becomes necessary therefore, in the 16 marks required. 100 Take the mean of the two breadths, taken at one-sixth from either extreme, and compare that with the main inside breadth, by ascertaining its decimal parts thereof, should those decimal parts be 75% no further allowance is to be made; but where it is more or less than 75 of the main breadth, as many hundred parts as the difference amounts to, must be added to or taken from the cubic contents, found as above, for the lower division of the vessel, to shew the true contents thereof. Divide the sum of the contents of the two divisions by 100, for the register measurement. PROPOSED BY THE REV. DR. INMAN, OF THE PRESENT TONNAGE COMMITTEE. The dimensions are supposed to be taken in English feet and decimals of feet. If inches are used, they must be turned into tenths and hundredths of feet, by dividing by 12, adding decimal ciphers if necessary. 1. Divide the whole girth by 2, and call the quotient the halfgirth for tonnage. 2. Divide the breadth by 2, and add the quotient or halfbreadth to the depth. Divide the sum by 2, and call the quotient the radius for tonnage. 3. From the length of deck subtract the half-breadth, and call the remainder the length for tonnage. * Measuring the Girth. The girth of the greatest transverse section to the height of the under surface of the tonnage deck may be taken by sweeping a chain under the false keel, either from forward or from aft, according to circumstances, and placing it in a vertical position at the extreme breadth of the ship; then, stretching it as tight as possible to opposite 'spots, marked on the sides at the height of the under surface of the tonnage deck, between which spots the breadth is taken. This measurement is easily taken at any time of tide, either when a vessel is lying in a tier or singly. Extreme Breadth at Deck. The extreme breadth at the tonnage deck is taken at the height of the under surface of this deck, by placing a stout straight board across the gunwale, or through two opposite ports, according to the size of the ship, so as to project sufficiently beyond the sides to allow two plumb-lines to drop clear of the water or broadest part of the ship. The distance between the lines gives the extreme breadth of the ship. The sum of the distances between the plumb-lines and the two spots marked on the side, exactly within the plumb-lines, being subtracted, the remainder will be the breadth required. Length of Deck. The length of the tonnage deck is taken by stretching a small line fore and aft, as tight as possible, on the upper surface of the deck, at a parallel and sufficient distance from the middle line of the ship, in order to clear the several hatchways and other obstacles that may present themselves. The line is then fastened at each end, and measured in this position. The places of the ends of the line are then squared over to the middle line of the ship, and the lengths forward and aft taken from the spots squared to, to the inside of the stem and 4. Multiply the half-girth for tonnage by the radius for tonnage, and multiply the product by the length for tonnage. Divide the last product by 80, and the quotient will be the required tonnage in English tons.* 5. The multiplication just described may be more easily performed by logarithms thus: Add together the logarithm of the half-girth for tonnage, the logarithm of the radius for tonnage, the logarithm of the length for tonnage, and the constant logarithm 8.096909; the sum (rejecting 10 from the index) will be the logarithm of the tonnage required. PROPOSED BY MR. RIDDLE FOR MEASURING THE INTERIOR CAPACITY OF SHIPS FOR TONNAGE. Take the depth at one-sixth of the length of the upper deck from the stem and the stern, and at the middle, from the under part of the deck to the ceiling at the timber strake, and measure the inside breadth at one-fifth, and four-fifths of the fore and aft depths, and at two-fifths of the midship depth, and the length, at the middle of the midship depth, from the aft part of the stem to the fore part of the stern post. Take the sum of the fore, the aft, and twice the midship depth, and also the sum of the breadths at the fore and aft sections, and twice that at the midship section. Multiply the product of these two sums by the length, all in feet, and the result, divided by 25-35 will be the interior capacity in feet. PROPOSED BY LIEUT. H. RAPER, R.N. OF THE PRESENT TONNAGE COMMITTEE. The length of the deck for tonnage, that is, the upper deck of two, or the middle one of three, from the stem to the stern-post stern-post. The sum of these additional lengths is then added to that already measured. The result is the length required. Depth. The depth abreast the pump-wellt is taken by fastening a line to the under surface of the deck at this station, applying it perpendicularly to the surface of the keelson, by placing one arm of a square well with the keelson and the other with the line. The line is then measured, and the distance from the surface of the keelson to the ceiling, close to the limber boards (measured in the direction of the line,) is added. Should this method be, in any case, difficult to be executed on account of lumber or stowage, the depth may be taken down the pump, or in any other way that seems most convenient, the proper allowances being made for the height of the ceiling above the point measured to. The first product is nearly the area in square feet of the greatest transverse section: ths of the second product is nearly the interior capacity in cubic feet of the ship up to the under surface of the tonnage deck. These results, in many cases, will be found extremely useful. + This depth might be taken, perhaps more advantageously, at the greatest transverse section, or as near thereto as possible. |