The accompanying illustrations show the methods recently adopted in the Austin dam construction for conveying material. E. W. Graves, engineer in charge of the work, says:
Pcrhas the most notable piece of machinery employed in the work is the overhead cableway, designed and furnished by the Lidgerwood Manufacturing Company of New York, which, owing to its efficient work, demands more than passing notice. From the natural conformation of the ground this was an ideal place for the location of this piece of michinery. The west bluff rises nearly vertical to a height of sixty-five feet above the crest of the dam, while the east bluff rises ten f et above the dam. This cable is suspended on two towers, the easterly one, in which is situated the hoisting engine, being seventy feet high, and the westerly one thirty feet high. The main cable on which the carriage moves is two and one-half inches in diameter, 1850 feet long and 1350 feet between points of support.
This is the greatest span of any hoisting cableway in existence. On the west side of the river and 1200 feet up stream from the dam is situated a limestone quarry, from which extends a gravity railroad along the west bluff directly under the cable. A carload of rock could be run from the quarry to the cable, taken up at once anil transported to denicks on any portion of the work.
A double track was used near the dam so that an empty car was ready to receive the empty skip, and a loaded car was also ready when the carriage came for a load. This gravity railroad was submerged as soon as the dam was raised five feet above low water, and recourse is now had to barges, carryirg twenty cubic yards of rock, which is brought to the side of the dam and there unloaded with a steam derrick. Under the cable at the easterly end of the dam extends the railroad bringing granite from the quarries, which can be taken from the cars and transported to any portion of the work in the same manner as the limestone. Mortar is mixed on the wall near the workmen, sand and cement being taken out by the cable. Loads of about five tons are usually carried. This cable is capiblc of supplying about 180 cubic yards of material per day, where the distance to be traveled is not more than 1000 feet.
The illustrations are two views of the big dam across the Colorado river at different periods of its construction, with the Lidgerwood apparatus in operation.