The thrower’s wheel is essentially a revolving vertical spindle, with a small round table at the top, beside which the thrower sits. The clay is handed to him in balls, and he throws it upon the whirling table between his knees. The table is put into motion either directly by the pressure of the workman’s foot on a lower table, or by some arrangement of straps and pedals. If the movement is given by the potter himself, as is still the case at Sèvres, and to some extent in China, there is the advantage that a more delicate and intimate control of the speed is possible. The movement of the clay under the potter’s hand is instinctively regulated by him. Every one has seen and marvelled at the wonderful process. The clay is first drawn up into a pillar, and then depressed into a flat cake, so that the circular arrangement of the particles may spread through the whole mass. The thrower then opens the hollow of the vessel with his thumbs, and proceeds to give it the desired shape, moistening his hands at intervals by dipping them into the slip. Small pieces are shaped between the thumb and first finger, either of one or of both hands. For larger pieces the whole hand and wrist is called into play, with the assistance, it may be, of a sponge. Still larger vessels are built up by piling on to the circular edge as it revolves strips of the clay. Delicacy of hand is of the greatest importance--the pressure applied and the movements of the fingers must be regulated by the nature of the clay, and especially by its greater or lesser plasticity. It is essential that the workman should not only press evenly and steadily on the clay as it rises, but that the speed of the rotation should have a definite relation to the rate at which he raises his hands. With a ‘fat’ or unctuous clay especially any irregularity of pressure will betray itself, and the marks will be more prominent after firing. This is the origin of the spiral ridges that we often see on the surface not only of common earthenware, but sometimes of high-class porcelain. To this cause are due the rings so characteristic of Plymouth porcelain; this ‘wreathing’ or ‘_vissage_’ is sometimes seen on Chinese porcelain also. When the thrower has finished his vessel, it is cut off from the table by a piece of thread or by a brass wire, and taken to the stoveroom to dry and harden. When sufficiently dry the vessel is placed on a lathe, and the turner shaves off all superfluous clay. The finer mouldings (using the word here in its architectural sense) may also be given at this stage, and sometimes the surface is shaped by a ‘profile’ of steel (it may be a piece from the blade of an old saw), which cuts the surface down to the desired shape. The shavings are carefully preserved and returned to the slip-house, to be blended with the new clay, the working qualities of which are thereby improved.