326 



REPORT ON NATIONAL MUSEUM, 1886. 



bottom of the quany, iu a liorizontal position along the bench, into the 

 roof, or perpendicularly into the floor, as desired." 



Plain quarry frame ia position for undercutting or gatlding. 



(4) GRINDING AND POLISHING MACHINES. 



In the larger works the griudiug and polishing already described is 

 now done by steam power. For Hat surfaces a circular, horizontally 

 revolving iron plate or grating, attached to the lower end of a vertical 

 shaft, with elbow joint, is used, the workman guiding it to any portion of 

 the surface he may desire by means of the handle; the abrading sub- 

 stance being sand or emery, as before. With felt attached to the plate 

 the same form of machine is also used for polishing. Blocks of such 

 size as ca'.i be handled by the workmen are usually ground upon hori- 

 zontally-revolving iron beds some 8 or 10 feet in diameter. 





Ingersol Standard Gadder at work. 



In making straight or only slightly-curved moldings the form is lirst 

 carved out with the chisel, and then a plate of cast iron, fitted as accu- 

 rately as iiossible, is made, by means of a long arm, to travel back and 

 forth over the stone with sand or emery, or putty powder and felt, as 

 the case may be. These arc called pendulum machines. The actual 

 labor is thus greatly reduced, and a higher and more lasting polish 

 obtained than is possible by the old hand methods. 



