520 



PEARL SPAR 



which E' rests, proceeds from /. When E' is raised, E sinks. The catch, c b, enters 

 with its front tooth into a slanting notch upon the upper edge of E, spontaneously 

 by the action of the spring e, whereby the opening, E, is shut. 



The small door, N, rises again with the front arm of the lever by the operation of 

 the weight Q, of itself, as soon as the catch is released by pressure upon c. 



The most important part of the whole apparatus is the drum, K, for the reception 

 and rounding of the bits of glass. It may be made of strong copper, or of hammered 



or cast iron, quite open above, and 

 pierced at the bottom with a square 

 hole, into which the lower end of 

 the long rod, t, is exac'tly fitted, and 

 secured in its place by & screwed 

 collector nut. The blunt point x 

 (fig. 1611) rests during the work- 

 ing in a conical iron step of tho 

 laboratory,./^. 1612. On the mouth 

 of the drum, K, a strong iron ring 

 is fixed, having a bar across its 

 diameter, with a square hole in its 

 middle point, fitted and secured by 

 a pin to the rod t, and turned by its 

 rotation. The vessel K, and its axle 

 t, are laid in a slanting direction ; 

 the axle rests in the upper ring z, at 

 the lower end of the rod I, of which 

 tho other end is hung to the hook 

 n, upon the mantel-beam, N. On 

 the upper end of t, the handle, s, is 

 fixed for turning round continuously 

 the vessel K while the fire is burn- 

 ing in the furnace, the fuel being 

 put not only in its bottom chamber, 

 but also into the holes F, o (fig, 

 1611). The firewood is made very 

 dry before being used, by piling it 

 in logs upon the iron bars 9, 10, 11. under the mantel-piece, as shown in figs. 

 1611, 1612. 



After the operation is finished, and the cover N is removed, the drum is emptied 

 of its contents, as follows : Upon the axle t, there is, towards K, a projection at u, 

 Alongside the furnace (fig. 1611) there is a crane, sr, that turns upon the step, s, 

 on tho ground. The upper pivot turns in a hole of tho mantel-beam, N. Upon the 

 horizontal arm, \v, of the crane there is a hook, y, and a ring, q, in which the iron 

 rod p is moveable in all directions. When the drum is to be removed from the 

 furnace, the crane, with its arm w, must be turned inwards ; the under hook of the 

 rod p is to be hung in the projecting piece u, and the rod I is lifted entirely out. 

 After this, by means of the crane, the drum can be drawn, with its rod t, out of the 

 furnace ; and, through the mobility of the crane and its parts p, q, any desired position 

 can be given to the drum. Fig. 1611 shows how tho workman can with his hand 

 applied to s' depress the axle t, and thereby raise the drum, K, so high that it will 

 empty itself into the pot i,, placed beneath. When left to itself, the drum on the 

 contrary hangs nearly upright upon the crane by means of the rod p, and may 

 therefore be easily filled again in this position. The manner of bringing it into 

 the proper position in the furnace, by means of the crane and the rod I, is obvious 

 from fig. 1612. 



The now well-rounded beads are separated from the pulverulent substance with 

 which they were mixed by careful agitation in sieves ; and they are polished and 

 finally cleaned by agitation in canvas bags. See ABLKTTE. 



PfiARIi BUTTONS. Pearl-button making is thus practised : the blanks are cut 

 out of the shell by means of a small revolving steel tube, the edge of which is t'oothed 

 as a saw, after which they are flattened or reduced in thickness by splitting, which 

 is aided by the laminar structure of the shell. At this stage, being held in a spring 

 chuck, they are finished on both sides by means of a small tool : the drilling is 

 effected by the revolution of a sharp steel instrument, which acts with great rapidity. 

 Ornamental cuttings are produced by means of small revolving cutters, and the final 

 brilliant polish is given by the friction of rotten-stone and soft soap upon a revolving 

 bench. 



P&A&Xi SPAR. A name commonly applied to crystallised dolomite exhibiting 

 Curved faces. 



