EXCAVATING THE RAW MATERIALS. 379 



is probably a maximum for fairly careful management of a difficult 

 quarry under Eastern labor conditions. 



At one Portland-cement plant in the Middle States a 20-foot lime- 

 stone-bed, overlain by 10 to 15 feet of shale and soil, is worked in open 

 cut. When this work was handled by contract, 18 cents per cubic 

 yard was paid for stripping, and 23 cents per ton for quarrying rock. 

 Haulage to the mill, only a quarter of a mile away, cost about 4 cents 

 per ton, owing to local difficulties. Quarry laborers here were worth 

 SI. 50 per day, and the following data on actual cost of quarrying were 

 obtained from one of the contractors. The items cover labor and sup- 

 plies for two men for two weeks, during which time the pair got out 

 300 tons of limestone. 



10 Ibs. dynamite at SO. 14 per Ib SI . 40 



i box caps at SO . 75 per box 0.19 



1 keg powder at SI . 50 per keg 1 . 50 



100 feet fuse at SO .45 per 100 feet .45 



Repairs, sharpening, etc . 60 



24 days' labor at SI . 50 per day 36.00 



Cost of quarrying 300 tons limestone $40 . 14 



Cost of quarrying, per ton limestone . 13 + 



" "stripping, " " " 0.07 



" " hauling, " " " 0.04 



Total cost limestone per ton SO . 24 



When it is necessary to mine the materials, the cost will be some- 

 what increased. Natural-cement rock has been mined at a cost equiv- 

 alent to 10 cents per barrel of cement; but the figure is attained under 

 particularly favorable conditions. The cost of mining and transpor- 

 tation may reach from this figure up to 20 cents per barrel. 



Costs of marl-dredging. The costs of dredging and handling marl 

 at several American cement-plants are given below : 



Plant 1. The marl- and clay-pits are about 3^ miles by track from 

 the mill. Both materials are covered by \ to 1 foot of earth, but 

 no water. A long cut is made into the deposit, into which cut cars 

 are run on light tracks. These cars, containing about 3000 Ibs. of 

 marl, are loaded by hand. The contract price for loading is 8 cents 

 per car for marl and 14 cents per car for clay, and these prices are equiv- 

 alent to a pay of $3.00 to $4.00 per day of 12 hours for each laborer 

 loading. Two engines are used, one for switching and making up trains 

 at the marl- and clay-pits, the other for hauling the trains to the 

 mill. The total cost for sufficient marl and clay for 1200 barrels 

 cement is : 



