At Panama the mosquito is almost an extinct animal, and though the heat there is sometimes trying, a run up to Culebra brings one to a dry and bracing atmosphere where a fresh breeze is almost always blowing. [18] During 1908 no less than one million dynamite charges were exploded. The steam shovel is the principal agent of excavation. It scoops out loose soil directly, but the basaltic rock has to be broken up first by blasting. One shovel will load 1,200 cubic yards of such materials upon the cars within the working day of 8 hours, an amount equal to 600 two-horse loads. For accelerating transportation railway trucks provided with flaps are used, which make of the whole train a single platform. At the rear of the train is a plough which can be drawn by a wire rope attached to a drum carried on a special car in the fore part of the train. When the train arrives at the dump the drum is started, and the plough, advancing, clears the 320 cubic yards of earth and rock from the 16 cars in 7 minutes. This is the Lidgerwood Unloader. Another important piece of machinery is the track-shifter, which picks up and relays the railway lines of the ever-shifting spoil-tracks. This remarkably successful contrivance was invented by an employee on the Isthmus, and is moreover manufactured there in the great workshops at Gorgona. [Illustration: FROM CULEBRA, LOOKING EAST TO DISTANT HILLS.] [Illustration: FROM CULEBRA, LOOKING EAST ACROSS THE CUT.] From Bas Obispo to Pedro Miguel, which constitutes the Cut, is a distance of about 9 miles, and excavation is so planned that a summit is maintained at Lirio, near Culebra, about half-way between these two points. On the north slope are[19] 21 steam shovels, loading cars on 14 tracks. These, when loaded, are hauled down-grade to the northern dumps at Tavernilla and elsewhere, or to the site of the Gatun dam, which is also a dump. Nearly 4,000 cubic yards of rock are carried to the dam daily, a distance of about 24 miles. The return up-grade is made with empty cars. On the southern slope about the same number of steam shovels are at work, the spoil being taken to the southern dumping grounds on the Pacific side, including the trestle dump for the breakwater to Naos Island. The spoil-trains follow one another at intervals of about three minutes, and if, from any cause, delay occur, the steam shovels, and indeed the whole process of excavation, is brought to a standstill. Any cause of delay is therefore reported at once by telephone to the Superintendent of Transportation at Empire, and all energies are at once directed to clearing the way. On the Isthmus everything gives way to the spoil-train, as in a city to the fire-engine. An excellent lesson both in the complexity and urgency of the transportation is afforded by a run through the Cut on a motor trolley in company with the Superintendent of the Department of Excavation. Constantly shunted from one track to