324 



REPORT ON NATIONAL MUSEUM, 1886. 



vary in direction from perpendicular to 50 degrees slant for putting 

 down the tunnel and angle cuts. If necessary the boiler can be left at 

 a distauce from the machine, the steam being conveyed by hose. 



Diamond. Cuannelii);: Machine. 



(3) GADDING AND GADDING MACHINES. 



The diamond gadder is shown on page 325. According the company's 

 circular the machine takes its name from the class of work for which it 

 was especially designed and which is known among quarriersas " gad- 

 ding." When the requisite channel cuts are made about a block of 

 marble to be removed, it is necessary to undercut the block in order to 

 release it. This is usually accomplished by drilling a series of holes 

 beneath it, and then, by wedges, the block is split from its bed. 



The machine is placed upon a platform on trucks arranged to run 

 upon a track. When adjusted for work it maybe braced by the pointed 

 legs shown. The boring apparatus is attached by a swivel to a perpen- 

 dicular guide-bar. This guide-bar is secured to the boiler behind it, 

 which forms the main support of the machine. Upon the guide-bar the 

 boring apparatus may be raised or lowered at pleasure, for the purpose 

 of boring a series of holes in a perpendicular line if desired. Upon the 

 swivel the boring apparatus may be turned, so as to bore in any direc- 

 tion within the plane of the swivel-plate, 





