POTTERY 



C07 



ounces in weight are reduced to one-third of their bulk by evaporation. The pint 

 of dry porcelain-clay weighs 17 ounces, and in its first pasty state 24, as just stated. 

 The dry flint-powder weighs 14 ounces per pint; which when made into a cream 

 weighs 32 ounces. To 40 measures of Teignmouth clay-cream there are added, 



13 measures of flint-liquor. 

 12 porcelain clay ditto. 

 1 Cornish stone ditto. 



The whole are well mixed by proper agitation, half dried in the troughs of the slip- 

 kiln, and then subjected to the machine for cutting up the clay into junks. The 

 above paste, when baked, is very white, hard, sonorous, and susceptible of receiving 

 all sorts of impressions from the paper engravings. When the silica is mixed with 

 the clay in the above proportions, it forms a compact ware, and the impression 

 remains fixed between the biscuit and the glaze, without communicating to either any 

 portion of the tint of the metallic colour employed in the engraver's press. The 

 felspar gives strength to the biscuit, and renders it sonorous after being baked ; while 

 the china-clay has the double advantage of imparting an agreeable whiteness and 

 great closeness of grain. 



"Wo must now proceed to a consideration of the manufacture. The clay being pre- 

 pared, is submitted to the potter, who employs at the present day a wheel of the same 

 description as that used in the days of Moses. 



Throwing is performed upon a tool called the potter's lathe. This consists of an 

 upright iron shaft, about the height of a common table, on the top of which is fixed, 

 by its centre, a horizontal disc or circular piece of wood, of an area sufficiently 

 great for the largest vessel to stand upon. The lower end of the shaft is pointed, 

 and runs in a conical step, and its collar, a little below the top-board, being truly 

 turned, is embraced in a socket attached to the wooden frame of the lathe. The shaft 

 has a pulley fixed upon it, with grooves for 3 speeds, over which an endless band 

 passes from a fly-wheel, by whose revolution any desired rapidity of rotation may be 

 given to the shaft and its top-board. This wheel, when small, may be placed along- 

 side, as in the turner's lathe, and then it is driven by a treadle and crank ; or when 

 of larger dimensions, it is turned by tho arms of a labourer. 



1643 



Fig. 1643 is the profile of the ordinary potter's lathe, for blocking-out round 

 ware, c is the table or tray ; a is the head of the lathe, with its horizontal disc ; a, b, 

 is the upright shaft of the head ; d, pulleys with several grooves of different diameters, 

 fixed upon the shaft, for receiving the driving-cord or band ; k is a bench upon which 

 the workman sits astride ; e, the treadle foot-board ; I is a ledge-board, for catching 

 the shavings of clay which fly off from the lathe ; A is an instrument, with a slide-nut 

 i, for measuring the objects in the blocking-out ; c is the fly-wheel, with its winch- 

 handle, r, turned by an assistant ; the sole-frame is secured in its place by the heavy 

 stone p ; /is the oblong guide-pulley, having also seA r eral grooves for converting the 

 vertical movement of the fly-wheel into the horizontal movement of the head of the 

 lathe. 



D is one of the intermediate forms given by the potter to the ball of clay, as it re- 

 volves upon the head of the lathe. 



In large potteries, the whole of the lathes, both for throwing and turning, are put in 

 motion by a steam-engine. The A'ertical spindle of the lathe has a bevel wheel on it, 

 which works in another bevel-toothed wheel fixed to a horizontal shaft. This shaft is 

 provided with a long conical wooden drum, from which a strap ascends to a similar 

 conical drum on the main lying shaft. The apex of the one cone corresponds to the 

 base of the other, which allows the strap to retain the same degree of tension, while 



