712. What is the difference between the thermometer and the barometer?
In the thermometer the column of mercury is much smaller than in the barometer, and is sealed from the air; while in the barometer the column of mercury is open at one end to atmospheric influence.
713. Why does the mercury in the thermometer, being sealed up, indicate the external temperature?
Because the heat passes through the glass, in which the mercury is enclosed, and expanding or contracting the metal within the bulb, causes the small column above it to rise or fall.
"Blessed is the people that know the joyful sound: they shall walk, O Lord, in the light of thy countenance."—Psalm lxxxix.
714. When does the thermometer vary most in its indication of natural temperature?
It varies more in the winter than in the summer season.