Proceedings of the Polytechnic Association. 743. 



either side for the passage of elevators where stationary engines are 

 to be employed for moving the elevators np and down, and for other 

 purposes. Half way between the stations a single shaft is to be sunk. 

 Let the work of excavation commence simultaneously at all the shafts, 

 and when the bottom shall be readied, let parties of as many men as 

 can work to advantage 2:0 on driftinof in line of the tunnel in both 

 directions from eacli of the shafts. This will give, for each party, a 

 section of 208 feet, or sixty-nine and one-third yards ; each lineal 

 yard gives forty cubic yards, making 2,773 cubic yards' excavation 

 per section. 



From Cressy's Encyclopedia of Civil Engineering, London, 1847, 1 

 quote estimates which iiave been derived from much experience of 

 the labor of excavation. By this, a man will excavate, ready for 

 removal, per day, 22.2 yards vegetable earth ; 14.92 yards loam ; 9 

 yards clay ; 6.67 yards stony earth ; 5.4 yards turfa ; 2.7 yards solid 

 rock. ]N^ow, let us take a section of solid rock, of which we shall 

 encoimter considerable, and which will require more time than any 

 other excavation. 2,773 cubic yards, at two and seven-tenths 'yards 

 per day, will require 1,027 days. If the party consists of twelve 

 men, which is by no means large, they will do the work in eighty- 

 seven days, or less than three months. Assuming wages at three 

 dollars per day, the cost per section will be $3,081, and a mile of 

 twenty-five sections, will cost $77,025 for excavating and preparing 

 the material for removal. It is said, and I think truly, that the 

 material will remove itself, i. e., it will command a price that will 

 pay for its removal. To facilitate the latter process and the advance- 

 ment of the work, the party of diggers will be followed up by other 

 parties, Avhose duty it will be to lay down the ways (of which there 

 will be four tracks — two for. way, and two for through passengers), 

 over which, by means of trucks, the material will be run to the ele- 

 vators, which, in turn, will raise it to the surface ; also to perform 

 the mason work, where masonry is required, and to finish up the 

 work generally. Thus, in four or five months, a single section will 

 be completed, and if each section is completed in five months, the 

 whole work will be done in tlie same time. It appears, then, as I 

 first stated, that, with ample means, and men provided beforehand, 

 the work can be accomplished in six months' time. I do not say 

 that it would be politic or profitable to rush so great a work through 

 in so short a time ; I only say that it is practicable. It might be 

 better to occupy a whole year or more ; but to procrastinate beyond 



