SEA WATER DENSITY AND DRAUGHT

•375

The foregoing method is not accurate in the case of ships and other
irregularly shaped bodies. A nearer approximation may be got by
assuming the ship to be a hydrometer and the distance between F.W.
and S.W. marks to represent the scale, the top edge of F W being 0
and the top edge of S W being 25, with the intervening distance divided
up proportionately.

F
MHMM
r
W_
[•' 2
o 5 en

2'

IO Q;

3"
,
U i5 H

4"

5;..

rv -?5 °

D

Fig. 15.

Assuming the distance between F.W. and S.W. marks to be 5 inches
and to be divided into five parts corresponding to 5, 10, 15, 20 and 25
of the hydrometer scale, then, as in Figure 15, when the dock water
density is 1005 the F.W. mark should be 1 inch clear of the waterline
and 2 inches clear when the hydrometer reads 1010, 3 inches clear for
1015, 4 inches for 1020, and 5 inches for 1025, the density when the
ship should be loaded to the top edge of the S.W. mark.

Example.—The distance between the F.W. and S.W. marks is

rw.

3*.

£ 6-

"° u»

-»:...!» s

« r
o

sw

?. 16.

7 inches in the case of Caledonian Monarch, what aDowance in draogat
would be made when loading her in dock water of density 1005?
The difference of draught is to 7 inches as the difference of density