24 A TREATISE ON DREDGES AND DREDGING 



Steam Punch. In the year 1854 Mr. Charles T. Harvey, the 

 designer and builder of the first New York elevated railroad, while 

 engaged in the construction of the St. Mary's Falls ship canal \\as 

 compelled to remove a ledge of solid rock, over 1000 cu.yds., encount- 

 tered on Lake Superior, just at the mouth of the canal. He had 

 only a dredge of very small capacity, which was of no use for such 

 work. He constructed a new machine which he called a steam punch, 

 described by Mr. Benjamin E. Buchmann, as follows: 



The machine consisted of a shaft, which, dropping, struck on 

 the submerged rock with a force of 20 tons per sq.in. a blow that 

 no rock could withstand. He used a wrought iron shaft 16 in. in 

 diameter and tapered down to 1 in. square steel-faced point. To 

 this was welded a socket formed out of the wrought iron fluke of 

 a propeller's wheel. Into this socket was keyed the end of a heavy 

 oak timber to form the punch or chisel, weighing altogether over 

 a ton, and striking a blow, as stated, of 20 tons per sq.in. By a 

 system of gauges and stops it was known when the punch had 

 penetrated below the desired depth, when it was moved a given 

 distance dropped again, until the submerged rock was broken into 

 such fragments as could be readily removed by the dredge. The 

 required machinery was mounted on a scow. It took 6 weeks to 

 break the ledge, which was from 1 in. to 3 ft. higher than the 

 required level. 



Thus the method of breaking subaqueous rock by falling weights 

 used in the Lobnitz machine was employed in the United States 

 some years ago. 



Lobnitz Rockcutter. Messrs. Lobnitz & Co. of Renfrew, Scotland, 

 have constructed a very efficient rock-cutting machine which has 

 been extensively used in difficult subaqueous excavations all over 

 the world. It was successfully employed in the deepening and 

 widening of the Suez Canal. The Lobnitz machine was illustrated 

 in Engineering from which this slightly condensed description 

 was taken. 



The machine (see Fig. 4) is built on the principle of a floating 

 pile driver; but the monkey of the latter is replaced by a heavy 

 rod of steel armed at its lower end with a renewable oiiival h-ad. 

 This steel ram or chisel may weigh complete from 4 to 20 tons and 

 is allowed to fall from a height of 6 ft. to 10 ft. on to the rocky 

 bottom to be excavated. The weight of the rani used depends not 

 only on the hardness of the rock, but also on the depth of the water, 



