EXCAVATION OF SUBAQUEOUS ROCKS 



31 



and preventing the bit from striking the rock in the successive 

 blows, was obviated by the introduction of a pump which forced 

 a jet of water into the drill holes for the purpose of cleaning them 

 of debris. 



Fig. 5 shows a modern plant for subaqueous drilling designed 

 and used by Mr. William L. Saunders for the removal of rock in 

 New York Harbor. It consists of an old scow or hulk, upon which 

 are housed the boiler room, the engine room and the blacksmith 

 shop, and a detached drill stage, which is, however, connected to the 



FIG. 5. Sa under 's Machine for Subaqueous Rock Excavation. 



boat by a gangplank. The drill stage chiefly consists of a wooden 

 platform supported by four adjustable legs sliding into castings, 

 so that they may be adjusted to any height and regulated according 

 to the tides, so as to have the platform always above the water- 

 level. The platform or stage is provided with slots cut both in 

 the longitudinal and transverse direction in order to allow the points 

 of the drills to go through. Located on the stages are two drilling 

 machines of the automatic-feed type mounted on tripods. They are 

 provided with an extension piece operating through a submarine 

 tube, which extends underneath the platform, and is used to direct 

 the blows of the drills. These drill stages will stand heavy blasting. 



