Some time passed before the precise design of the tunnel could be settled. At first it was decided to describe a spiral in the peak so as to accommodate the level of the Argentine division with that of the Chile section of the line. The tunnel was to be driven from either end by the engineers of the respective railways, which were two distinct undertakings. The two armies were to meet at mid-tunnel immediately beneath the famous statue of Christo Redentor, commemorating the treaty of peace between Argentina and Chile, which stands upon the boundary line of the two countries in the pass above. On the Argentine side the camps for the tunnel works were established at Las Cuevas, about 1½ miles below the portal. When boring was commenced the engineers’ advance was threatened. The depth of the loose, friable earth eroded from the peaks above, which had accumulated during the flight of centuries, proved much greater than was supposed. This entailed most elaborate timbering to prevent the roof caving in and burying the excavators. As all lumber had to be brought up from Mendoza, for this desolate region is far above the timber line, heavy delays arose pending the arrival of the wood. Then they had to move forward warily foot by foot, as the detritus proved treacherous to handle. The engineers ploughed their way through this material for 300 feet, and felt relieved when at last they struck solid rock, which they rightly thought was the main body of the mountain. Elaborate arrangements were made to drive ahead more rapidly, but when the mass had been penetrated for nearly 200 feet the engineers received another rude shock. The rock was false. What they had fondly thought to be the mountain itself was merely a huge crag which had become detached and had slipped down bodily. Here was a critical dilemma. The work was far too risky for aught but expert tunnel-builders--engineers who had made a speciality of such undertakings, and who were possessed of competent ability and facilities to cope successfully with any contingency likely to develop. As a result of careful deliberations it was decided to hand the whole tunnel--lock, stock and barrel, from end to end--to one firm. Selection fell upon the British engineers, Messrs. C. H. Walker & Company, who rescued the famous Severn tunnel from flood, and successfully completed it in the face of unheard-of difficulties. These engineers at once attacked the problem boldly. It was found that the false rock on the Argentine side extended for no less than 1,670 feet, so that it must have been a most violent shiver of Nature, indeed, which let loose that mountain spur. The situation, however, was grasped so completely that within two years the range was pierced.