duryee] CEMENT INVESTIGATIONS IN ARIZONA. 379 
FUEL. 
An extensive but undeveloped deposit of bituminous coal is located 
about 17 miles from the San Carlos dam site. There is a wagon trail 
to within about G miles of the coal beds, but after leaving the wagon 
trail the only means of access was found to be a bridle path over the 
hills. About ten years ago numerous prospectors' locations were 
made in the district, and shafts were sunk at a sufficient number of 
localities to prove the deposit to be of considerable extent. Most of 
the shafts have become filled with debris, but several were entered to 
depths of 15 to 30 feet. Tlw showed the body of coal to be in beds 
having a dip of about 60°, the beds being from 5 to 10 feet in thick- 
ness, not of solid fuel, but showing seams of good coal interlaid with 
seams of slate and waste. In the bottom of the deepest shafts was 
found a good body of coal in a solid bed perhaps 5 feet thick. It was 
reported that at the time the prospecting was done on the claims some 
30 tons were transported by wagons to the Southern Pacific Railroad 
and used in the locomotives, but that the cost of mining and trans- 
porting it to the railroad, with the crude means available at the time, 
was about $20 per ton. 
Cement could be burned with the coal. The right to mine the coal 
for the use of the Government in this work could be secured readily 
and at a nominal cost. The cost of mining and transportation to San 
Carlos would, however, be high. In general practice 120 pounds of 
coal dust are used in burning 1 barrel of Portland cement. 
Taking as a basis coal delivered at the dam site at $10 per ton, 
limestone at 40 cents per ton, and clay at $1.25 per ton, the cost of 
manufacturing Portland cement at the dam site would approximate 
$2.75 per barrel. The cost of erecting a plant with an output of 300 
barrels of cement every twenty-four hours would be $75,000. Sup- 
posing the amount of cement to be required in the construction of 
the dam to be 50,000 barrels, the cost per barrel, if made at the site, 
would be approximately as follows: First cost of plant, $75,000; cost 
of manufacturing 50,000 barrels, at $2.75, $137,500; total cost, 
$212,500; cost per barrel, $4.25. 
With reference to the degree of reliability to be placed upon Port- 
land cement made in new localities, it may be said that the manufac- 
ture of this material has been put upon a scientific basis, such that 
the manufacturing chemist can predict the grade of cement to be 
made from the given materials, and, by means of analyses of various 
rocks, can calculate suitable mixtures to produce the required result. 
The uniform system of testing cements recommended by the Ameri- 
can Society of Civil Engineers affords a reliable means of determining 
the intrinsic merits of the product. The old method of buying 
cements on the reputation of the maker has been succeeded by tests 
for determining the actual value. Portland cements of American 
