SHIP BUILDING. 
The next dimension is tlie extreme 
breadth, and without repeatinp; (lie propor- 
tions which various authors have mentioned, 
all alike erroneous as to fixed datas, we will 
give the extreme breadths of the above 
■ships, which upon trial have been found ty 
answer their intended purposes by that 
construction. 
Breadth, moulded 
Breadth, extreme 
Guns. 
' 
Sloop. 
18 
110 
98 
74 
50 
36 
rt. In. 
;->‘i 0 
o^ 10 
Ft, In 
49 0 
19 1( 
Ft. In 
48 0 
48 8 
Ft. In, 
39 10 
40 6 
Ft. In. 
,'57 6 
38 i 
Ft. In. 
29 0 
29 6 
Brea'dth, moulded 
Breadth, extreme 
Tonnage of Merchant Ships. ' 
1257 
1000 
818 
544 
441 
329 
Ft. In. 
41 1 
42 C 
Ft. In, 
.37 4 
38 0 
Ft. In, 
3.5 4 
36 0 
Ft. In. 
31 4 
32 0 
Ft. In. 
28 6 
29 0 
Ft. In. 
27 0 
27 6 
The letigth of the keel for tonnage, as 
was before observed, is produced from the 
former dimension, and a length given by a 
rule, although long established, is very de- 
fective, and the tonnage or burthen of the 
vessel, as it is sometimes called, is said to 
be produced therefrom. It may be there-i 
fore readily seen that those two dimensions 
only cannot possibly give any true burthen, 
for those two dimeu.sions may be alike in 
twb vessels of the greatest difference in 
their construction imaginable, for one vessel 
may be so constructed from the samfigdi- 
mensions as to be very sharp under her 
load draught of water with a very quick 
rising, to possess the requisite qualities for 
fast sailing, as the sloop of war, while an- 
other vessel keeping the dimensions, the 
same may be constructed as full under 
water as the most burthensome merchant 
ships. Sometimes the production of this 
rule is called builders tonnage, as a contra- 
distinction to the true tonnage, and by this 
result builders are paid a certain price per 
ton for building any vessel. 
THE RULE FOR CASTING THE TONNAGE. 
In the royal navy, is to take the length on 
a stiaight line along the lower side of the 
rabbit of the keel from a perpendicular or 
square from the back of the main stern 
post, at the height of the wing transom, to a 
perpendicular or square at the height of the 
upper deck (and middle deck of thiee- 
decked ships) from the fore-part of the 
stern. The only difference in merchant 
ships is to take this lengtli as before from 
the back of the main post at the height of 
the wing-transom to the same height for- 
w'ard to the fore side of the stern ; then 
flora the length between those perpendicn- 
lars subtract three-fifths of the exfrerne 
breadth for the rake forw’ard, and two 
inches and a half for every foot the w'ing- 
traniom is high above the lower part of the 
rabbit of the keel for the rake abaft. The 
remainder is the length of the keel for 
tonnage. 
Although this is the dimension sought, 
yet to show the fallacy of acquiring this 
tonnage the whole of the rule shall be here 
subjoined. 
Then multiply the length of the keel for 
tonnage by the extreme breadth, and the 
product by half that breadth, and divide the 
whole by 94 j the quotient will be the 
tonnage. 
This extreme breadth to be taken from 
the outside to the outside plank or thick- 
stuff, in the broadest part of the ship, either 
above, on, or below the wales, deducting 
from the said thickstuff' or plank all that it 
exceeds the thickness of the plank of the 
bottom, which shall be accounted the ex- 
treme breadth ; so that the moulding 
breadth, or breadth of the frame, will then 
be less than tlte ejttreme breadth so founds 
