Fig. 11.—Showing paper cross and glass almost filled with water and cross placed over the top.
The vibration of the glass when emitting the notes explains this phenomenon, although the reason that the cross should remain still when you rub beneath one of its arms is too technical for explanation here.
Fig. 12.—A “light” experiment.
A Light Experiment
Why do we wear white clothes in extreme heat and dark clothes in the winter? To this question every one will answer that white clothes absorb less heat than black, and that we therefore feel the rays of the sun less.
Quite true; and yet, how is it that Polar bears and other Arctic creatures exposed to such extreme cold are clothed in white?
The fact is that not only does white absorb less heat, but it serves to retain heat, and a white coat preserves the natural warmth in the animal’s body. This is exemplified by the following experiment, for which only a tumbler is required.
Choose a glass with the lower part faced, as in [Fig. 12]. Color these faces black and white alternately, a little India ink serving for the former and some crushed chalk and water for the latter.