HYDROMETER

361

Specific gravity of sea water=

weight of 1 cub ft sea water
weight of 1 cub. ft, fresh water
1025

1000

= 1-025

The density of mercury is 849 Ibs per cubic foot and the

0 .„ . (849X16) oz. per cub. ft.

Specific gravity of mercurv =-------------------:—----------

* & J * 1000 oz per cub. ft.

= 13-6

BUOYANCY.

Buoyancy is due to the supporting power of the water. All bodies
when immersed in water exhibit an "apparent" reduction in weight.
Everybody experiences this sensation when lying in &. bath of water
and Archimedes has the credit of being the first man to establish and to
apply the theory in practice.

It is necessary to recall to mind the following information when
working examples on buoyancy.

1 cub. ft. fresh water = 62\ Ibs. = 1000 oz.

1 cub. ft. salt water

2240 Ibs.

224 gallons

1 ton fresh water

1 ton salt water

1 cub. ft.

64 Ibs.

1 ton

1 ton fresh water

36 cub. ft.

35 cub. ft.

1728 cub. ins.

Experiment—Find the volume of an object, say a sphere,

3

(see "Mensuration," page 349). Suspend the sphere from a spring
balance, as in Figure 2 and note its weight* Immerse the sphere in

Fig,