EXCAVATION OF SUBAQUEOUS ROCKS 



23 



striking the bottom of the cylinder with sufficient force to cause 

 injury to the cover, a supplementary steam-pipe taking its supply 

 from the valve casing is led into the bottom of the cylinder. 

 This arrangement insures a constant supply of steam at boiler 

 pressure on the lower side of the piston, acting on it as a brake 

 or buffer in its descent. The cylinder is securely bolted to 

 the carrier. This is formed of two square-edged vertical beams 

 12 x 12 in. and a framing of 12 x 6 in. timbers bolted together so 

 as to provide a rigid structure. The carrier slides vertically 

 along the faces of the tower and has its movements controlled by 

 a steam winch. The carrier is secured from transverse movement 

 on the tower by a T-shaped guide or retaining piece bolted to its 



FIG. 3. Scott & Godsir Rockcutter. 



vertical timbers and sliding between the two upright timbers of 

 the tower and engaging them on their back. The carrier is provided 

 with a shelter for the steam cylinder and the operator. Also the 

 tower consists of two vertical beams, each 12 in. square in cross 

 section, set 1 ft. apart and braced with diagonal struts and steel grip 

 wires. The steam is conveyed from the boiler to the cylinder by 

 means of a 4-in. steam pipe, trunnioned at the joints to permit of 

 vertical movement. One of the pipe-lengths is guided by a quad- 

 rant piece and is reinforced by timber bolted to the pipe, which 

 bears against the quadrant. 



In regard to the efficiency of this machine, it was found that 

 when the moving parts weigh about 3| tons and the stroke of the 

 piston is about 4 ft., making 60 strokes per minute this apparatus 

 w r ill break more than 30 cu.yds. of solid rock per day. 



