A scraper is provided to keep the disk clean and prevent sticking.
The rectangular scraper (42) began in S.D.
The salt is collected from the surface by means of a sort of wooden scoop or scraper, but in spite of every precaution some of the soil on which it is produced is inevitably taken up with it, communicating a red or grey tint.
The typical implements are flint points or spear-heads, left smooth and flat on one side, as struck from the cave, pointed and edged from the other side; a scraper treated in the same way, but with edge rather upon the side than at the end, as in the succeeding Solutrian and Madelenian epochs.
Many beetles make a hissing or chirping sound by rubbing a "scraper," formed by a sharp edge or prominence on some part of their exoskeleton, over a "file" formed by a number of fine ridges situate on an adjacent region.
The file may be on the head - either upper or lower surface - and the scraper formed by the front edge of the prothorax, as in various wood-boring beetles (Anobium and Scolytus).
Sharp; in the stag-beetle larva a series of short tubercles on the hind-leg is drawn across the serrate edge of a plate on the haunch of the intermediate legs, while in the Passalid grub the modified tip of the hind-leg acts as a scraper, being so shortened that it is useless for locomotion, but highly specialized for producing sound.
Earthy matter and other matter precipitated and fallen on the copper double bottom may be dislodged by a slowly revolving scraper - say every twelve hours - and ejected through the bottom discharge cock; and thus the heating surface of the copper bottom will be kept in full efficiency.
Owing to the fact that at temperatures between its melting and boiling point zinc has a strong affinity for iron, it is often contaminated by the scraper while being drawn from the condenser, as is shown by the fact that the scraper wears away rapidly.
The metal is then removed from the walls with the aid of an iron scraper, and the whole mass poured into a sheet-iron tray, where it solidifies.
In Malwa a flat scraper is employed, a small piece of cotton soaked in linseed oil being attached to the upper part of the blade, and used for smearing the thumb and edge of the scraper to prevent adhesion of the juice; sometimes water is used instead of oil, but both practices injure the quality of the product.
The first of these resemble an ordinary reverberatory furnace by having a flat bed which, however, has the form of a circular disk mounted on a central shaft, and receives a slow movement of rotation from a water-wheel or other motor, so that every part of the surface is brought successively under the action of the fire, the charge being stirred and ultimately removed by passing under a series of fixed scraper arms placed above the surface at various points.