W VARIOUS INVENTIONS. 



tools for this purpose before I set the workmen to make them. 

 Any day will suit me, except Monday, the 8th of February. 

 The sooner the better, as I cannot set to work to make the tools 

 until we have arranged the plan. 



"I am, Sir, 



"Your humble servant, 



KD. T." 



The successful completion of the Mont Cenis Tunnel 

 in 1871 was mainly due to an ingenious application of 

 combined mechanical force to boring tools, before limited 

 to man's strength ; but the applied principle existed 

 sixty years ago, and though not so perfect in detail, yet 

 more comprehensive. Trevithick's high-pressure steam 

 boring engine enabled him to penetrate the rock five 

 times as fast as the quarryrnan's power. Ten holes, 

 2^ inches in diameter, 4 feet deep, could be bored in an 

 hour, and he sagaciously suggested that in quarrying 

 the limestone for the breakwater, a row of holes should 

 be bored by his engine 4 feet in from the face of the 

 rock, 2J inches in diameter, 4 feet deep, and 12 inches 

 apart; and by dropping into each hole two half-round 

 pieces of iron, to be driven asunder by a steel wedge, 

 large blocks would be forced off without the use of gun- 

 powder. The high-pressure steam-puffer having bored 

 the stone, moved itself toward the broken mass, lifted 

 it into waggons, and again changing its powers from 

 steam-crane to steam-locomotive, conveyed it to the 

 port, and lifted it into the ship's hold. The whole 

 operation was thus aptly described by the inventor, 

 who then counted on contracting for the breakwater 

 work : " Steam machinery will accomplish more than 

 nine- tenths of all the work, besides saving the expense 

 of all the gunpowder." 



