On the Pacific side the concrete handling plant was somewhat different. Instead of cableways there were great cantilever cranes built of structural steel. Some of these were in the shape of a giant T, while others looked like two T's fastened together. Here the clamshell dippers were run out on the arms of the cranes to the storage piles, where they picked up their loads of material. This was put in hoppers large enough to store material for 10 cubic yards. The sand and stone then passed through measuring hoppers and to the mixers with cement and water added. After it was mixed it was dumped into big buckets on little cars drawn by baby steam locomotives, which looked like overgrown toy engines. These little fellows reminded one of a lot of busy bees as they dashed about here and there with their loads of concrete, choo-chooing as majestically as the great dirt train engines which passed back and forth hard by. The cranes would take their filled buckets and leave empty ones in exchange, and this was kept up day in and day out until the locks were completed. When the plant was removed from Pedro Miguel to Miraflores, a large part of the concrete was handled directly from the mixers to the walls by the cranes without the intermediary locomotive service. The cost of the construction of the locks was estimated in 1908 at upward of $57,000,000. But economy in the handling of the material and efficiency on the part of the lock builders cut the actual cost far below that figure. On the Atlantic side about a dollar was saved on every yard of concrete laid--about $2,000,000. On the Pacific side more than twice as much was saved. Before the locks could be built it became necessary to excavate down to bed rock. This required the removal of nearly 5,000,000 cubic yards of material at Gatun. Then extensive tests were made to make certain that the floor of the locks could be anchored safely to the rock. These tests demonstrated that by using the old steel rails that were left on the Isthmus by the French, the concrete and rock could be tied together so firmly as to defy the ravages of water and time. A huge apron of concrete was built out into Gatun Lake from the upper locks at that place, effectively preventing any water from getting between the rocks and the concrete lying upon them. CHAPTER V THE LOCK MACHINERY