November 2, 1837, 12 years after its commencement, there had been expended 264,000 pounds, and it \vas then estimated to require an additional sum of 350,000 pounds to complete it, which, if correct, will .

make the final cost 614,000 pounds, or near four times the original estimate. As before observed, we are not to consider the two cases as parallel, though there is a degree of similarity, which very naturally excites attention when looking for some guide in the expense of other work.

Estimated Expense of Harlem Tunnel.

11,000 cubic yards earth excavation on shores, at 14 cents, $ 1,540 2,000 cubic yards rock excavation on shores, at $1 50, 3,000 24,000 cubic yards excavation of mud in river, at 1,- 24,000 3.000 cubic yards excavation of sand in river, at 1, - 3.000 4,000 cubic yards excavation of rock in river, at 5, - 20,000

Coffer Dam.

240,000 feet, board measure, white oak timber, at $35, - - $ 8,400 700,000 feet board measure, white pine timber, at 20, - - , 14,000 380,000 feet, board measure, yellow pine timber, at 30, - 11,400 10,000 lineal feet round piling, at 20 cents, - 2,000

$35,800

CROTON AQ.UEDUCT. 169

20,000 pounds wrought iron bolts, straps and spikes, at 12 cents - - $2,400 Pin timber and treenails 250 Carpenter and other work, framing, sinking, and securing frame - 30,000 Driving 2,000 feet lineal of sheet piling, at $2 4,000 Driving 320 round piles at $3 cubic earth filling and embanking coffer, at 40 cents - 380,000 yards 15,200 Estimated cost of pumps, steam engines, and working, (very uncertain) 30,000 Removing frame, piling, earth of dam from the channel estimated 15,000 133,610 1,800 cubic yards brick masonry, at $18 - 32,400 8,000 cubic yards stone masonry and concrete, in abutments and tunnel, at $10 - 80,000 460 cubic yards coping and side facing of tunnel, at $30 - 13,800 2 entrance houses on abutments - 2,000 128,200 6,500 cubic yards stone embankment in river, between abutments and shores, at $2 - 13,000 3,000 cubic yards foundation and protection wall, at $2 50 - 7,500 20,500 700 tons iron pipes, delivered, at $75 - - 52,500 Lead, yarn, tallow, and work putting down 3,100 feet, at $4 - 12,400 13,000 cubic yards earth covering, at 20 cents - - 2,600 2 pipe chambers, as per detailed estimate of December, 1837 - 15,642 Waste cocks and man hole plates - 7,500 90,642