The Dying Fish
Cut a piece of deal into a prism about four inches long, and color two of the sides black or dark blue, painting the remaining side white. Sharpen one end into a small triangular point, and paint two eyes and a mouth thereon, so that the completed figure appears as in [Fig. 17].
Now, if you put this in a basin of water very heavily salted, you will find that the fish floats quite naturally, as in [Fig. 18], whilst if you place him in a basin of plain fresh water, he will immediately turn on his back and float dead, with the white side uppermost, as in [Fig. 18a].
Fig. 17.—Completed figure of fish.
Fig. 18.—“Dead” fish floating.
Fig. 18a.—Fish on his back.
This is caused by the greater density of the salt water acting upon the prism.