A. The sides of the mercury rub against the glass tube, and are delayed by it, so that the middle part rises faster than the sides.
Q. Why is the mercury concave when it is falling?
A. The sides of the mercury rub against the glass tube, and are delayed by it, so that the middle part sinks faster than the sides.
Q. What effect does a thunder-storm produce on the weather?
A. Thunder is generally preceded by hot weather, and followed by cold and showery weather.
Q. What effect does a sudden change produce on the weather?
A. A great and sudden change (either from hot to cold, or from cold to hot) is generally followed by rain within 24 hours.
Q. Why is a sudden change from hot to cold followed by rain?
A. The cold condenses the air and its vapour; which, being condensed and squeezed out, falls in rain.