The Cup of Tantalus.
This pretty toy may be purchased at any optician’s for seventy-five cents. It consists of a cup in which is placed a human standing figure concealing a syphon or bent tube, with one end longer than the other. This rises in one leg of the figure to reach the chin, and descends through the other leg, through the bottom of the cup to a reservoir beneath. If you pour water in the cup it will rise in the shorter leg by its upward pressure, driving out the air before it through the longer leg; and when the cup is filled above the bend of the syphon, that is, level with the chin of the figure, the pressure of the water will force it over into the longer leg of the syphon, and the cup will be emptied, the toy thus imitating Tantalus, of mythology, who is represented by the poets as punished in Erebus with an insatiable thirst, and placed up to the chin in a pool of water, which, however, flowed away as soon as he attempted to taste it.
The Magic Whirlpool.
Fill a glass tumbler with water, throw upon its surface a few fragments or thin shavings of camphor, and they will instantly begin to move, and acquire a motion both progressive and rotary, which will continue for a considerable time. During these rotations if the water be touched by any substance which is at all greasy, the floating particles will quickly dart back, and, as if by a stroke of magic, be instantly deprived of their motion and vivacity.
In like manner, if thin slices of cork be steeped in sulphuric ether in a closed bottle for two or three days, and then placed upon the water, they will rotate for several minutes, like the camphor, until the slices of cork, having discharged all their ether, and become soaked with water, they will keep at rest.
If the water be made hot the motion of the camphor will be more rapid than in cold water, but it will cease in proportionately less time. Thus, provide two glasses, one containing water at fifty-eight degrees, and the other at two hundred and ten degrees; place raspings of camphor upon each at the same time; the camphor in the first glass will rotate for about five hours, until all but a very minute portion has evaporated, while the rotation of the camphor in the hot water will last only nineteen minutes. About half the camphor will pass off and the remaining pieces, instead of being dull, white and opaque, will be vitreous and transparent, and evidently soaked with water. The gyrations, too, which at first will be very rapid, will gradually decline in velocity until they become quite sluggish.
The stilling influence of oil upon waves has become proverbial. The extraordinary manner in which a small quantity of oil instantly spreads over a very large surface of troubled water, and the stealthy manner in which even a rough wind glides over it must have excited the admiration of all who have witnessed it.
By the same principle a drop of oil may be made to stop the motion of the camphor, as follows: Throw some camphor, both in slices and in small particles, upon the surface of water, and while they are rotating dip a glass rod into oil of turpentine. Then allow a single drop thereof to trickle down the inner side of the glass to the surface of the water. The camphor will instantly dart to the opposite point of the liquid surface, and cease to rotate.