If we observe the waves continually approaching the shore, we must be convinced that this apparent motion is not one in which the water has any share: for were it so, the waters of the sea would soon be heaped upon the shores, and would inundate the adjacent country; but so far from the waters partaking of the apparent motion of the waves in approaching the shore, this motion of the waves continues, even when the waters are retiring. If we observe a flat strand when the tide is ebbing, we shall still find the waves moving towards the shore.
Ornamental Fountain Clocks.
It is the same cause (that which produces the deceptive appearance of a progressive motion in the waves of the sea) which makes a revolving cork-screw, held in a fixed position, seem to be advancing in that direction in which it would actually advance if the worm were passing through a cork. That point which is nearest to the eye, and which corresponds to the crest of the wave in the former example, continually occupies a different point of the worm, and continually advances towards its extremity.—This property has lately been prettily applied in ornamental clocks. A piece of glass, twisted so that its surface acquires a ridge in the form of a screw, is inserted in the mouth of some figure designed to represent a fountain. One end of the glass is attached to the axle of a wheel, which the clock-work keeps in a state of constant rotation, and the other end is concealed in a vessel, designed to represent a reservoir or basin. The continual rotation of the twisted glass produces the appearance of a progressive motion, as already explained, and a stream of water continually appears to flow from the fountain into the basin.
Facility of Swimming.
The lighter the body is in relation to its magnitude, the more easily will it float, and a greater proportion of the head will remain above the surface. As the weight of the human body does not always bear the same proportion to its bulk, the skill of the swimmer is not always to be estimated by his success; some of the constituent parts of the human body are heavier, while others are lighter, bulk for bulk, than water. Those persons in whom the quantity of the latter bear a greater proportion to the former, will swim with a proportionate facility.
Common Mistake in Cooling Wine.
When ice is used to cool wine, it will be ineffectual if it be applied, as is frequently the case, only to the bottom of the bottle; in that case, the only part of the wine which will be cooled is that part nearest the bottom. As the application of ice to the top of the bottle establishes two currents, upwards and downwards, the liquid will undergo an effect in some degree similar to that which would be produced by shaking the bottle. If there be any deposit in the bottom whose weight, bulk for bulk, nearly equals that of the wine, such deposit will be mixed through the liquid as effectually as if it had been shaken. In such cases, therefore, the wine should be transferred into a clean bottle before it is cooled.
Why Cream collects on the surface of Milk.
There are numerous familiar effects which are manifestations of the principle now explained. When a vessel of milk is allowed to remain a certain time at rest, it is observed that a stratum of fluid will collect at the surface, differing in many qualities from that upon which it rests. This is called cream; and the property by which it ascends to the surface is its relative levity; it is composed of the lightest particles of the milk, which are in the first instance mixed generally in the fluid; but which, when the liquid is allowed to rest, gradually arise through it, and settle at the surface.
Directions engraved upon the Common Weather Glasses absurd.