A

thunder

glass

or

storm

glass

is

a

barometer

that

uses

water

instead

of

mercury.

A

glass

globe

with

a

spout

is

filled

with

water.

High

pressure

pushes

down

on

the

water

in

the

spout,

causing

it

to

drop.

Water

rises

up

the

spout

when

there

is

low

pressure.

These

barometers

were

often

used

on

small

ships

in

the

1800s

so

sailors

could

tell

when

a

storm

was

coming.

A

storm

glass

Spout

Globe