philosophy, a cavity in the surface of water, or other fluid, with an elevation above thereof.

The waves of the sea are of two kinds, natural and accidental. The natural waves are those which are exactly proportioned in size to the strength of the wind, whose blowing gives origin to them. The accidental waves are those occasioned by the wind's re-action upon itself by repercussion from hills and mountains, or high shores, and by the washing of the waves themselves, otherwise of the natural kind, against rocks and shoals: all these causes give the waves an elevation, which they can never have in their natural state.

Mr. Boyle has proved, by numerous experiments, that the most violent wind never penetrates deeper than six feet into the water; and it should seem a natural consequence of this, that the water moved by it can only be elevated to the same height of six feet from the level of the surface in a calm: and this six feet of elevation being added to the six feet of excavation, in the part whence that water so elevated was raised, should give twelve feet for the utmost elevation of a wave. This is a calculation that does great honour to its author: for count Marigny measured carefully the elevation of the waves near Provence, and found, that, in a very violent tempest, they arose only to seven feet above the natural level of the sea, and this additional foot in height he easily resolved into the accidental shocks of the water against the bottom, which was, in the place he measured them in, not so deep as to be out of the way of affecting the waves; and he allows that the addition of one fifth of the height of a wave, from such a disturbance from the bottom, is a very moderate alteration from what would have been its height in a deep sea; and concludes, that Mr. Boyle's calculation holds perfectly right in deep seas, where the waves are purely natural, and have no accidental causes to render them larger than their just proportion. In deep water, under the high shores of the same part of France, this author found the natural elevation of the waves to be only five feet; but he found also, that their breaking against rocks, and other accidents to which they were liable in this place, often raised them to eight feet high.

We are not to suppose, from this calculation, that no wave of the sea can rise more than six feet above its natural level in open and deep water; for waves immensely higher than these are formed, in violent tempests, in the great seas. These, however, are not to be accounted waves in their natural state; but they are single waves formed of many others: for in these wide plains of water, when one wave is raised by the wind, and would elevate itself up to the exact height of six feet, and no more, the motion of the water is so great, and the succession of the waves so quick, that, during the time this is rising, it receives into it several other waves, each of which would have been at the same height with itself; these run into the first wave, one after another, as it is rising; by this means its rise is continued much longer than it naturally would have been, and it becomes terribly great. A number of these complex waves arising together, and being continued in a long succession by the continuation of the storm, make the waves so dangerous to ships, which the sailors in their phrase call mountains-high.

Wave-offering, in Jewish antiquity, a sacrifice offered by agitation, or waving, towards the four cardinal points of the compass.