Encyclopaedia Britannica, or, a Dictionary of arts, sciences, and miscellaneous literature : enlarged and improved. Illustrated with nearly six hundred engravings > Volume 19, Scripture-SUG

292
Tonnage ef a great deal more. In confirmation of this, it is thought
3. Ship. 4-Ia/^ <-11 lir\tnc i'\£ (lllTYS. Wlttl
proper to fubjoin the dimenfions of feveral ihips, with
the tonnage calculated therefrom.
SHIP-BUILD IN G.
Tonnage
Real tonnage
806 109(5 Tonnage ij,
984 1670 a shlP-
i. Audacious of feventy-four guns.
Length on the gun deck
Length of the keel for tonnage
Extreme breadth
Depth of the hold
C" afore
Launching draught of water j
, r C afore
Load draught of water -t
The weight of the {hip at her launching
draught of water
The weight of the furniture
168 f. O in.
138 o
46
J9
12
I7
20
21
1509 t. 6781bs.
120 1500
Weight of the fhip at her light water
mark
Weight of the (hip at her load water
1629 2178
mark
2776 498
Real burthen
1146 560
By the common rule.
Length of the keel for tonnage
Extreme breadth
138 f. o in.
46 9
Produ6t
Half the extreme breadth
6451
23
94)150803
Tonnage according to the common rule 1604 643
Real burthen - - * 1146 560
Difference
458 83
132!. 8 in.
105 O
38
16
2. An Eaji Indiaman.
Length between the perpendiculars for¬
ward and aft
Length of the keel for tonnage
Extreme breadth - -
Depth in hold
Launching draught of water { abaft
r afore
Load draught of water -j
The weight of the {hip at her launching
draught of water - 6021. 2ii61bs.
The weight of the furniture - 50 124
Weight of the {hip at her light water
mark - - 653
Weight of the {hip at her load water
mark - - ^37 1670
7
11
19
20
O
O
10
10
8
8
Real burthen
Keel for tonnage
Extreme breadth
By the common rule.
984 1670
105 f,
38
Product
Half extreme breadth
3999
19
94)75810
Difference
J?8 574
3. A Cutter.
Length of the keel for tonnage
Extreme breadth
Lauching draught of water
Load draught of water "Fabaft
The weight of the cutter at her launch-
ing
Weight of the furniture
58f. oin.
29 o
5 10
9 8
9 0
12 o
147 t. 640lbs.
9 !99
Weight of the cutter at her light water
mark - - 839
Weight of the cutter at her load water
mark - - 266 1970
Real burthen - - 1101131
By the common rule.
Keel for tonnage
Extreme breadth
58 f.
29
Product
Half extreme breadth
1682
I4i
94)24389
Tonnage by the common rule
Real tonnage
259 1024
no 1131
Difference
148 2133
The impropriety of the common rule is hence mani-
feft, as there can be no dependence on it for afcertaining •
the tonnage of veffels.
We fhall now fubjoin the following experimental me¬
thod of finding the tonnage of a {hip.
Conftrua a model agreeable to the draught of the Exp^men
propofed Ihip, to a fcale of about one-fourth of an inch ta] meth0d
to a foot, and let the light and load water lines beofdeter-
marked on it. Then put the model in water, and load mining the
it until the furface of the water is exaftly at the light
water line ; and let it be fufpended until the water
drains off, and then weighed. Now fince the weights of
fimilar bodies are in the triplicate ratio of their homolo¬
gous dimenfions, the weight of the Ihip when light is,
therefore, equal to the product of the cube of the num¬
ber of times the {hip exceeds the model by the weight
of the model, which is to be reduced to tons. Hence,
if the model is conftrudled to a quarter of an inch fcale,
and its weight expreffed in ounces j then to the con-
ftant logarithm 0.4893556, add the logarithm of the
weight of the model in ounces, and the fum will be the
logarithm of the weight of the {hip in tons.
Again, the model is to be loaded until the furface of
the water coincides with the load water line. . Now the
model being weighed, the weight of the {hip is to be
found by the preceding rule : then the difference be¬
tween the weights of the fhip when light and loaded
is the tonnage required;
5