In

1714,

Gabriel

Fahrenheit

invented

the

mercury

thermometer.

In

this

thermometer,

the

mercury

expanded

up

the

tube

when

it

was

warm,

and

dropped

back

down

when

it

was

cold.

The

mercury

thermometer

is

still

used

today.

An

early

mercury

thermometer

(right)

and

a

modern

one

(left).

Comparison

of

Fahrenheit

and

Celsius

temperature

scales

Fahrenheit

Celsius

Boiling

point

212˚F

100˚C

Freezing

point

32˚F

0˚C