EXCAVATION OF SUBAQUEOUS ROCKS 



33 



be provided either with one or several drills. Fig. 7 shows a single 

 drilling machine as built by the Ingersoll-Sergeant Co. This consists 

 of an ordinary scow or pontoon supporting a wooden frame similar 

 to the one used in connection with a pile-driving machine, and 

 erected on the front edge of the pontoon. A drill of large size is 

 mounted on these leads. The leads can be made of any desired 

 length and are equipped with a hand and power feed, used for raising 

 the drill in the leads or guide. An automatic lead is provided for 

 feeding the drill down as it cuts away the rock. The drill and feeding 

 arrangements are fastened to a spud which is placed between wooden 



178 



FIG. 7. Ingersoll Drilling Scow. 



or iron guides for the purpose of raising or lowering the apparatus 

 to suit the various depths of water. The drilling is done through a 

 tube which rests on the rock and supports the weight of the spud 

 carrying the drill. The drill steel is hollow and has a valve placed 

 in it near the bottom, which acts the same as a pump, the cut- 

 tings being forced up and out at the top. The drill is operated 

 from a boiler located on the deck of the scow. 



To blast large quantities of rock in a comparatively short time, 

 more powerful machines are employed. These consist of scows 

 carrying a whole battery of drills, together with their equipment. 

 In such a case the boiler must be proportionate to the work required 



