BUILDING AND ORNAMENTAL STONES. 319 



machines for doin<^ this work are now in nse. In general they may be 

 said to consist of an iron frame-work some 2i feet high, with a hori- 

 zontal knife-edge upon its upper edge. Against tliis knife is made 

 to work by means of a treadle another knife, curved in outline, which is 

 thrown upward again by means of a spring, after being brought down 

 by the treadle-movement. At right angles to this knife-edge, on one 

 side of the machine, an iron arm projects toward the workman; this 

 arm has notches cut into it for the different sizes of the slate. The dif- 

 ference between the two kinds of machines is said to consist chiefly in 

 the arrangement of the cutting-knife, one working as stated above 

 while the other revolves on an axle something in the manner of an 

 ordinary corn cutter. 



Slates are sawn by means of an ordinary circular saw, such as is used 

 in sawing lumber, and are planed by machines such as are used in 

 planing metals, as are other soft stone. Some of the hard slates used 

 for tiling have to be cut by means of circular saws with teeth of black 

 diamond.* 



(7) KINDS OF FINLSH. 



The more common kinds of finish applied to stone are described be- 

 low ; the figures on Plate IV being drawn from samples in the national 

 collections. 



(1) Rock face. — This is the natural face of the rock as broken from 

 the quarry, or but slightly trimmed down b^- the pitching tool. As in 

 this and all the figures given, it is frequently surrounded by a margin 

 of drove work. 



(2) Fointed face. — In this finish the natural lace of the rock has been 

 trimmed down by means of the sharp pointed tool called a point. It is 

 used principally for exterior work, as in the walls of a buihling. Two 

 common styles of pointing. are shown. 



(o) Ax-liammer€(lfacc.—T\i\& finish is produced by striking upon the 

 surface repeated blows with a sharp-faced hammer, called an ax or pean 

 hammer. It closely resembles the next, but is coarser. Used in steps, 

 house trimmings!, and other exterior work. 



(4) Patent hammered. — This finish is i)roduced by striking repeated 

 blows upon the smooth surface of the rock with the rough-faced imple- 

 ment called a patent hammer. Five grades of fineness are commonly 

 recognized, the 4-cut, C-cut, 8-cut, 10-cut, and 12-cut surfaces, made by 

 hammers composed of four, six, eight, ten, and twelve plates, respect- 

 ivel}". A very common finish for the finer kinds of exterior work. 



(5) Bush hammered. — This finish resembles closely the tooth chiseled 

 or very fine pointing. It is used mostly on soft stone. (See descriptions 

 of bush and patent hammers on p. 329.) 



* Detailed aud very closely resembling accounts of the methods of working slate 

 are given by F. W. Sperr, in Eeport Tenth Census, Vol. X, pp. 38-42, and E. Prince, jr., 

 report D 3, Vol. i, pp. 138-143, 2d Geol. Survey, Pennsylvania. To these the reader 

 is respectfully referred. 



