The power of a river to abrade the soil over which it flows, so far as water is by itself capable of doing so, must depend upon its volume and velocity, and the degree of hardness of the material acted upon.
This accumulation of earthy and stony debris in the bottom of the ice, gave it a rough and grinding lower surface, which enabled it to abrade the land over which it passed much more effectively than ice alone could have done.
If a stream be swift enough to carry off not only all the detritus descending from its slopes, but to abrade its bed effectively besides, a steep-sided gorge develops.
On either side or above it other stones, moving at different rates, are made to abrade it, so that its top and sides may be planed and scored.
Like all streams which are the outlets of lakes, the Niagara flows out of Lake Erie clear of sediment, as from a settling basin, and carries no tools with which to abrade its bed.
Waves abrade the shore and strew the debris worn from it over the lake bed.
When the reef has risen to wave base, the waves abrade it on the windward side and pile to leeward coral blocks torn from their foundation, filling the interstices with finer fragments.
In the cleaning operations care should be taken to scratch or abrade the bran as little as possible, for this reason: The outer coating of the bran is hard and more or less friable.
But when the dies are rotated from right to left to bring them to the end of the bolt again, C, D will be rubbed by the thread, which tends to abrade them and thus destroy their sharpness.
If the bore of the emery wheel itself were made a tight fit to the spindle it would abrade the spindle in being put on, and the pressure of the fit if any would tend to split the wheel.
If, however, the surfaces are pressed together sufficiently to abrade the hard skin from the cast iron, a rapid cutting immediately takes place, which is very difficult to remove.
If it be removed by blows it becomes damaged, and damage is likely to be also caused to the shaft, while the surfaces having to slide in contact under the pressure of the fit the surfaces abrade and compress, and the fit becomes impaired.
The tools of the ice thus acquired in the process of plucking are quickly frozen into the lowest ice layers, and being now dragged along the floor they abrade in the same manner as does a rasp or file.
Those particles which come in contact with the bottom or sides of the channelabrade its surface so as ever to deepen and widen the valley.
