ALL Mensuration is to be done by the Swedish foot; and the vessel's burthen to be marked down in lasts, each to be considered in weight equal to eighteen skeppund iron weight, or 18 times 320 lb. Swedish.
The vessel's length to be measured on the highest water-line when loaded from the fore part of the rabbet of the stem to the aft part of the rabbet of the stern-post.
The ship's breadth is to be measured in mid-ships without-board close up to the main wale.
The height to be measured from the surface of the water without-board, up to that mark which determines how deep the vessel will swim when completely loaded.
Multiply these three admeasurements by each other, and divide the product by 112, should the vessel be of the usual shape, and neither too full nor too sharp at the stem and stern: if the vessel is sharper the divisor must then be greater, and if fuller a little less, as pointed out to the measurer in the separate instructions.
If the necessary provision, water, wood, and utensils for the voyage, should not be on board when the ship is measured, and which weight does not actually belong to the burthen that the vessel is measured to carry, then it is necessary to deduct from the calculated burthen of lasts as follows:
|On a vessel of 350||lasts is allowed||11||lasts deduction;|
Should one or more of the necessary cables not be on board when the vessel is measured, then the following deductions are to be made:
|For an 18||inch cable||25||skepppund;|
|All is iron weight.|
Should one or more anchors be wanting, their weight is to be deducted in proportion to the vessel's size.
If the vessel's sails are not on board, the deduction from its number of lasts is to be as follows:
|On a vessel of 350||lasts||14||skepppund;|
|All iron weight;|
If the vessel is built to carry guns constantly, and that none, or part of them only, are on board, then a deduction for cannon, carriages, gun-tackling, &c. is as follows:
|For a 12||pounder with its requisites||13||skepppund;|
|All iron weight;|
Should the vessel, when measured, have its ballast on board, then that weight must be ascertained, and added to the number of lasts found; but it is best to measure the vessel before it is ballasted, if convenient.
The ship's measurer having duly considered the foregoing circumstances, and in consequence thereof ascertained the vessel's proper tonnage to a certain depth, fore and aft, when loaded, he is then to make an entry of the foregoing in the Book of Admeasurements given him for that purpose, which book is run through and sealed with the seals of the Court of Aldermen and the Custom-House: he is also to enter the number of lasts requisite to immerse the vessel, progressively, from one foot at the beginning of the loading till when completed, and also to set down how deep she lies fore and aft when unloaded. — He is to deliver copies of the same with specific calculations, admeasurements, and deductions, of all this, to the Court of Aldermen and Board of Customs within two days after measured, that the same may be examined and sanctioned.
Should there be any-thing to be observed by the parties, the same must be made known at the respective places, within eight days after the delivery, at the expiration of which time the ship's register will be made out, and the approved calculation of the measurer annexed to the same, and to be kept on board as the ship's inventory. The same is to be entered with all the calculations in bound paged books, and alphabets thereunto annexed, in the Court of Aldermen and at the Custom-house.
Whereas vessels when old and soaked through by the water, cannot carry so much as when new, it is therefore requisite to measure the vessel every tenth year in like manner as expressed in the twelfth section.
INSTRUCTIONS for the ship's measurer for the better performance of his duty.
He is to provide himself with a five or six-foot rod, and a two-foot rule, which are to be divided into decimals, that is, each foot into ten parts or inches, and each inch into ten parts or lines: he must also be provided with a broad tape of about 80 alnar or 160 feet long, and about an inch wide: which, being painted on both sides with oil-colour, is to be marked with feet, and may for conveniency be wound up on a roller.
The rod and rule are divided into decimals on account of their ease in calculation, as the number of feet, inches, and lines are multiplied by each other as integers, and the decimals are separated from the integers by means of a comma, which by instruction and a little practice is made plain.
He must also be provided with a plummet of about two pounds weight, and a line of four or five fathoms in length.
When the length and breadth of the vessel are taken, it is necessary to measure that part of the height which by the loading is to be immersed.
1. OBSERVE how many feet and inches the vessel lies deep all around when quite empty, and call that place the discharging line.
2. ASCERTAIN a certain height on the stem and stern-post, to which it is to be immersed when loaded, and term that place the loading line.
It is fastest, or most accurate, to measure these heights with the rod, as the numbers marked down on the stem and stern are not always to depended on; besides, foreign measures differ from ours.
3. A vessel being very seldom so situated that the difference between the discharging line and the loading line is alike fore and aft, therefore the two distances are to be added together, and that halved, which shews to what depth the whole body will be immersed when loaded, and which I shall term immersing height.
As the tonnage or number of lasts depends on that column of water which the vessel occupies in consequence of the pressure of the loading, therefore the solid contents of that part which is between the discharging line and the loading line must be ascertained.
If the vessel is square-built, that is, at both ends of the same breadth as midships, its cubical contents would then be found, by multiplying the length, breadth, and height to be immersed, by each other; the product multiplied by 62 lb. which is about the weight of a cubic foot of water in our ports, would give the number of pounds which such a vessel could carry; and this product divided by the number of tons reckoned to a last, that is, 18 times 320 lb. or 5760, would give the burthen in lasts.
To shorten this operation, divide 5760 lb. by 62 lb.; the quotient 92,9, or 93, may be adjudged a general divisor for larger or smaller vessels, when the length, breadth, and the immersed height, are multiplied by each other.
But as ships or vessels never are thus shaped, but roundish at the ends, and more sharp at the discharging line that at the loading line, 93 cannot always serve as a proper divisor, because the calculation would them give a greater number of tons than the vessel could carry; therefore the divisor must be greater, and greater for sharp than full vessels.
The divisor for the solid contents close by the loading line must also be less than the divisor used for the whole immersion, because a vessel is always fuller at the loading line; and the divisor for the solid contents close by the discharging line must be greater than the divisor which is used for the whole depressure, because a vessel is always sharper at the discharging line than at the loading line, 93 cannot always serve as a proper divisor, because the calculation would then give a greater number of tons than the vessel could carry; therefore the divisor must be greater, and greater for sharp vessels than full vessels.
The divisor for the solid contents close by the loading line must also be less than the divisor used for the whole immersion, because a vessel is always fuller at the loading line; and the divisor for the solid contents close by the discharging line must be greater than the divisor which is used for the whole depressure, because a vessel is always sharper at the discharging line than at the loading line: therefore this method of measuring depends on a proper divisor, suitable to the vessel's more or less fullness at its ends.
HAVING made calculations from the draughts of sundry ships, and trial on several vessels, it has been found that in full-built vessels, which have nearly the same breadth all the way, and are very full at the ends, the divisor for the number of lasts for the whole immersed heights is to be 104; for the number of lasts near to the loading line 98; and for the number of lasts near to the discharging line, the divisor is to be 108.
GERMAN Galliots and Galleasses, and some Dassar yachts and English colliers, which generally have a long and continued breadth, and are very full at both ends, the divisor for finding the number of lasts for the whole immersed height must be 108; to find the number of lasts near the loading line, 99; and to find the number of lasts near the discharging line, the divisor must be 114.
COMMON English barks and cats, and other vessels which are similar with regard to fullness, the divisor for the whole immersed height is 110; by the loading line 100; and by the discharging line 117.
For vessels in common, which are neither too full nor too sharp, as are generally out Mediterranean traders, especially the larger sort, the divisor for the immesing height is 112; by the loading line 101; and by the discharging line 120.
VESSELS which are a little sharper, and yachts in common, which are rather broad, but their sides all along possessing a deal of curvity and not very sharp at the ends, the divisor for the whole immersing height is 115; by the loading line 102; and by the discharging line 124.
VESSELS which are very sharp fore and aft, as are our brigantine and schooners, the divisor for the whole immersing height is 122; by the loading line 104; and close by the discharging line 133.
To facilitate the foregoing rules, I shall here give the divisors at one view in the following order:
|To what Class belonging.||For the whole Immersing Height.||Number of Lasts close to the Loading Line.||Number of Lasts close to the Discharging Line.|
MODE of applying the foregoing, viz.
SUPPOSE a vessel's extreme length from stem to stern by the loading line to be 132 feet, its extreme breadth without, close under the lower wale, 34 feet, or depth when empty aft 11,25 feet, and fore 9 feet, but that the loading line or depth in the water when loaded = 19 25/100 feet, and fore = 18 feet; subtract 11,25 from 19, 25, remains 8 feet; subtract 9 from 18, remains 9 feet. 8 and 9 added together make 17, half of which, 8,5, is the whole immersing height which is to be immersed in the water.
|Multiply the Length||134|
|by the Breadth||34|
|Multiply this . . .||4556|
|by the Immersing Height||8,5|
If the vessel should come under the denomination of the 4th Class, with regard to fullness and sharpness, then the divisor for the whole immersing height is 112:
|112)||38726(345 96/112 lasts;|
The different wights of these articles, agreeable to regulation, are
|For||Provision, water, &c.||10½ lasts;|
|Eight four-pounders||48 ditto;|
|Skeppund 91½||is||5 2/100 lasts;|
|Lasts ascertained||345 86/112|
|Remain about||330 1/5 lasts;|
|and Fore||18 ditto.|
To find how many lasts are requisite to sink the vessel down at the beginning, or at the close of the loading:
The divisor for the discharging line, or when the vessel lies empty, is for the 4th Class put down to 120; and for the loading line 101.
The length and breadth multiplied by one another, divide by 120;
|120)||4556( = 38 lasts;|
Divide also 4556 by 101.
|101)||4556||( = 45 11/101 lasts;|
SUPPOSE that this ship or a similar one has the bottom so constructed, that it cannot lie straight on the water without ballast, or some other weight in the hold, it must then be measured when the same is on board; and suppose that it then lies deep aft 13,38 feet, and fore 10,79 feet, its depth fore and aft when loaded as before, therefore 13,38 from 19,25 is 5,87, and 10,79 from 18 is 7,21: add 5,87 and 7,21 gives 13,08, the half of which, 6,54 feet, is the whole immersing height.
Now as length and breadth are supposed to be the same, therefore multiply 4556 by 6,54.
As the vessel is considered under the same Class as before, use therefore the same divisor, that is, 112.
It now remains to know the weight of the ballast. — For that purpose, take on board so much of the cargo, of iron, boards, and other things, that the vessel may not overset when the ballast is taken out. — Suppose now, that what has been taken on board, of the cargo, sinks her down = 13,25 and 11,24. Now when the ballast is taken out, the depth aft is 11,1 feet, and fore 10 feet: subtract 11,1, from 12,25, remains 2,15 feet, which the vessel is lightened aft by taking out the ballast: subtract 10 from 11,24 remains 1,24, which the vessel is lightened fore: add 2,15 and 1,24 together, make 3,39, the half of which is 1,69; which is the height that the vessel is lightened by taking out the ballast. Multiply 4556 by 1,69,
|12,0)||7699,64||(64 16/100 lasts;|
The foregoing method with respect to measuring and calculating, and to form a proper idea with regard to vessels fulness and sharpness, depends chiefly on practice, and to pay attention to the greater or less continuance of breadth; so that although a vessel may appear full fore and aft, its fulness ought to be considered less, when the midship body does not continue far fore and aft, and in consequence to judge with propriety to what Class she belongs, so as to fix on a suitable divisor.
From a vessel's situation when loaded it is known if it has more or less on board than the burthen mentioned in the ship's register: because if the loading marked in the register is below the surface of the water, it has then more on board; and if above the surface, it has less than contained in the register. As there may be a difference of 3 or 4 lasts in 100 lasts, owing perhaps to the measurer's want of skill, especially if a new beginner, and before he is will versed in his duty;
It has therefore been though proper to remedy this evil by making an allowance in favour of the owner, viz.
|On vessels of 600||lasts burthen||16||lasts;|
If it be required to know what quantity of sundry commodities answers to the burthen of 22½ lasts, it is necessary to know, that a last is equal to 17 barrels Government pitch, or 15 barrels Finland tar, or 15 barrels Cagliari salt, or 16½ barrels St. Ube's salt, or 1½ fathom sound birch wood, &c.
|Inches Broad||Alnar* Length||Dozen per Last and Thickness in Inches.|
|1 Inch||1¼ Inch||1½ Inch||1¾||2 Inches|
|8||6||18½ doz.||14¾ doz.||12¼ doz.||10½ doz.||9¼ doz.|
The quantity of goods taken out of a vessel may easily be known by the above Tables.
For instance, if a vessel is become half a foot lighter at any time during the discharging of half the cargo, and it is found by the rule page 74 that the weight taken out is eqal [sic] to 21 lasts; if Cagliari salt has been discharged, then have (as 15 barrels make a last) 315 barrels been discharged. In like manner if the vessel during the course of taking in the same half of her cargo has been pressed down half a foot, then in the same manner may be calculated that a burthen of 21 lasts has been taken on board; and if tar, 315 barrels are taken: if the cargo consists of deals, as for example of 7 yards length, 1½ inch thick , and of sundry breadths, then has about 200 dozen been taken on board, and so on.
It sometimes happens, that a vessel is loaded deeper than ordinary, suppose half a foot deeper than the loading line, and consequently has taken 22½ lasts more than contained in the register; nevertheless, she ought not to be called of 352 lasts burthen, but remain of 330 lasts: it is only requisite to take notice how much deeper she swims than what the register expresses; as at another time she may happen not to be loaded up to the determined water-line. In the autumn, and when squally weather is expected, it is not customary to load so deep as in the spring and summer.
Transcribed by Lars Bruzelius
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