At times the work is exasperating. Perhaps the surveyor who has been imprisoned for months on end in an inhospitable country has been driven to his wits’ end to find a practicable location which is immune from the many disturbances of Nature. By dint of supreme effort finally he discovers a route which he congratulates himself to be absolutely safe, only to receive a rude awakening. In the survey of a new line through the Rockies, the mountains barring the engineer’s path had achieved an unenviable reputation, owing to the frequency and severity of the avalanches that tore down their steep slopes every spring. The surveyor reconnoitred that mountain chain from end to end, observed every path that the slides had been known to take, searched local records and questioned aged inhabitants to make himself acquainted thoroughly with the conditions. At last he concluded that he had elaborated a path for the railway which was beyond the destructive efforts of the periodical visitations and work was commenced. Yet in the first spring, while the construction train was crawling along with a load of excavated spoil from the mountain-side, the slipping snow departed from its accustomed path, and in its descent caught the unlucky train, threw it into the gulch some distance below, ripped up the metals, buried the grade beneath thousands of tons of debris, and obliterated every vestige of the work. The surveyor must be a man not to be daunted very easily in his enterprise, not to be cast down by heart-breaking failures, and who has the capacity to gather tangible assistance from apparently insignificant trifles. The search for a rift through a frowning mountain wall often is galling in its hopelessness. When the first Canadian trans-continental line was being forced towards the Pacific coast, the crossing of the Rocky, Selkirk and Gold ranges puzzled the surveyors acutely. Walter Moberly, a surveyor to the manner born, was deputed to complete the conquest of the Gold or Columbia Range. The obvious path to follow was along the bank of the mighty Columbia River, and this was taken by Moberly. Yet the Gold Range had to be threaded somewhere and somehow, though it appeared to defy penetration. He spent months wandering up and down the river, enduring hardships indescribable, seeking for the slightest breach through that terrible wall, wide enough to carry a pair of metals, but no gateway could he find. [Illustration: BUILDING THE LOFTIEST BRIDGE IN THE WORLD The Fades Viaduct spanning the Sioule River in France, 1,526 feet long. The two masonry towers are each 304 feet in height. The central span, 472 feet in length, was built out from each tower. The railway line in the centre of the bridge is 440 feet above the river.]