This attribute is of great use in the animal and vegetable kingdoms. The rising of the sap is one instance of the latter.
Experience in hydrostatics can be easily applied to amusing little experiments. For instance, as regards the syphon, we may make an image of Tantalus as per illustration (fig. 69). A wooden figure may be cut in a stooping posture, and placed in the centre of a wide vase, as if about to drink. If water be poured slowly into the vase it will never rise to the mouth of the figure, and the unhappy Tantalus will remain in expectancy. This result is obtained by the aid of a syphon hidden in the figure, the shorter limb of which is in the chest. The longer limb descends through a hole in the table, and carries off the water. These vases are called vases of Tantalus.
The principle of the syphon may also be adapted to our domestic filters. Charcoal, as we know, makes an excellent filter, and if we have a block of charcoal in one of those filters,—now so common,—we can fix a tube into it, and clear any water we may require. It sometimes (in the country) happens that drinking-water may become turgid, and in such a case the syphon filter will be found useful.
Fig. 68.—Molecular attraction.
The old “deception” jugs have often puzzled people. We give an illustration of one, and also a sketch of the “deceptive” portion (figs. 70 and 71). This deception is very well managed, and will create much amusement if a jug can be procured; they were fashionable in the eighteenth century, and previously. A cursory inspection of these curious utensils will lead one to vote them utterly useless. They are, however, very quaint, and if not exactly useful are ornamental. They are so constructed, that if an inexperienced person wish to pour out the wine or water contained in them, the liquid will run out through the holes cut in the jug.
To use them with safety it is necessary to put the spout A in one’s mouth, and close the opening B with the finger, and then by drawing in the breath, cause the water to mount to the lips by the tube which runs around the jug. The specimens herein delineated have been copied from some now existent in the museum of the Sèvres china manufactory.
The Buoyancy of Water is a very interesting subject, and a great deal may be written respecting it. The swimmer will tell us that it is easier to float in salt water than in fresh. He knows by experience how difficult it is to sink in the sea; and yet hundreds of people are drowned in the water, which, if they permitted it to exercise its power of buoyancy, would help to save life.
Fig. 69.—Vase of Tantalus.