The engineers tried innumerable expedients to preserve the line from these erratic attacks, but without any material success for some time. At last they decided to provide the river with an artificial embankment, and to lay the track well back from the waterway. Trainloads of huge masses of stone were brought to the vulnerable points and pitched at the foot of the embankment, which was raised to a height well above flood-level. Thousands of tons of stone were dumped in this manner, and it was found that it afforded complete protection, because the water could not dislodge the masonry pitching to eat its way into the soft earth beneath. The artificial dyke solved the problem of how to keep the rushing, boisterous Mendoza within bounds. Avalanches and snowslides were another constant menace. Their accustomed paths had to be noted carefully and then studiously given a wide berth. These convulsions are of impressive severity in the Andes, and the impetus the slides gain, owing to the steepness and length of the declivities down which they tumble, imparts terrific force to them. When a slender railway stands in their path it is caught up like straw and scattered in all directions. Possibly the landslides are more to be dreaded than the movements of the snow. In the Andes the denuding forces of Nature are exceptionally heavy. Many a mountain slope which, from a cursory inspection, looks substantial and solid, upon closer investigation proves to be merely a thick layer, perhaps many feet in thickness, of soft detritus. The slightest vibration is sufficient to set the mass in motion, and it slides slowly and irresistibly downwards. At some places it was found impossible to avoid such unstable ground, so the engineers ingeniously cut a passage through the soft rubble, taking care to reach the solid mountain flank beneath upon which to build the track, while the detritus was held back by means of massive concrete masonry walls. Under such circumstances it is imperative that the track should be of the most solid character, if it is designed to fulfil the conditions of a trunk highway. The road bed is well built, laid with metals to a metre-gauge, and ballasted heavily. All earthworks are carried out on liberal lines, and the bridges are built throughout of steel. When the main range is gained the line becomes more devious, the banks are sharper and more numerous, the short tunnels and the bridges across the rivers more frequent, for the location caused the line to swing from bank to bank as being more economical construction than to blast and carve a way for the line through the solid rock of the cliffs. At places the rises became so abrupt as to defy operation by adhesion. Then short lengths of rack where cog-wheels on the locomotive mesh with a toothed rail laid between the ordinary rails, and working similar to a rack and pinion, had to be inserted to enable the train to climb upwards.