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ON MERCANTILE STEAM TRANSPORT ECONOMY. 117 
- In this Table it will be observed that the twelve vessels, A, B, C, &ce. 
to M, are all of the same builders’ tonnage O.M., namely 1000 tons; that 
we have three vessels (A, B, C) whose length is four times the breadth of 
beam ; three vessels (D, E, F) whose length is six times the breadth ; three 
vessels (G, H, 1) whose length is eight times the breadth; and three vessels 
(K, L, M) whose length is ten times the breadth ; and that, in’ each set of 
three vessels, the load-draught of water is taken at two-thirds of the breadth, 
half the breadth, and one-third of the breadth; so that in this Table we have 
a gradation of proportions, the length varying from four times to ten times 
the breadth, and the load-draught varying from two-thirds to one-third of 
the breadth, which limits embrace nearly all the proportions of shipping in 
mercantile use. The arbitrary elements of construction on which the calcu- 
lations (Table A) have been prosecuted, are explained in the various head- 
ings. It will be observed that the freeboard (column 5), or non-immersed 
depth above the load-draught line, has in each case been taken at one- 
fortieth of the length, plus one-twelfth of the breadth of beam. There is no 
recognized rule for the determination of this element. Constructors of ship- 
ping follow their own rules or their own caprice in determining freeboard, or 
the position of the construction load-line. The above combined proportions 
of length and breadth have been adopted, as giving a progression, which, it 
is believed, will meet the ordinary allowance of freeboard at which loaded 
ships of all sizes are sent to sea. The various elements of construction 
(columns 7 to 16) are believed to be closely approximate to ordinary prac- 
tice ; and the ratios of nominal tonnage to actual weight-carrying capability, 
shown in columns 17 to 20, are therefore approximately such as would result 
from the ordinary build of shipping. 
Now, on comparing the ratios which result from the constructive propor- 
tions of the ships A, B, C, &c., M, we have the following results :—lIst, it ap- 
pears (see columns 17 to 20), that, taking builders’ tonnage at 100, the ratio 
of register tonnage varies from 85 to 51 in ships (A, B, C) of which the 
length is four times the beam, and from 94: to 63 in ships (K, L, M) of which 
the length is ten times the beam; that is, taking the extreme cases embraced 
within the limits of this Table, a ship of type K will have a register tonnage 
of 94 tons for every 100 tons builders’ measure ; but a ship of type C will 
have only 51 tons register for each 100 tons builders’ measure. It also ap- 
pears (see columns 17 and 19), with reference to )uilders’ tonnage O.M., 
taken at 100, that the capability for carrying weight fluctuates from 131 tons 
weight down to 33 tons weight per 100 tons of builders’ measure O.M., or a 
ship of 1000 tons builders’ tonnage of the type A will have four times the 
weight-carrying capability that is afforded by a ship of 1000 tons builders’ 
tonnage of the type M. 
With reference to register tonnage (gross), new measure, under the Act of 
1854, taken at 100, it appears (see columns 21 and 23) that the capability 
for carrying weight varies from 177 tons down to 52 tons per 100 tons of 
register tonnage; or a ship of 1000 tons gross register tonnage of the type 
A will have nearly 33 times the weight-carrying capability that is afforded 
by a ship of 1000 tons gross register tonnage of the type M. 
_ With reference to weight tonnage, or the capability of ships to carry 
weight, it appears (see columns 25, 26, 27) that, with the proportions of 
ship A, each 100 tons of weight-carrying capability will require a vessel of 
76 tons builders’ measure O.M., or 65 tons gross register tonnage; but 
with the proportions of ship M, each 100 tons of weight-carrying capability 
will require a vessel of 303 tons builders’ measure O.M., or 191 tons gross 
Tegister tonnage. 
