Some practical facts are furnislied by the experience of the workmea engaged in the construction of tlie new Central raihvay over the máin range of mountains in Peru. The line starts from Lima, in latitude 12 degs. The summit tunnel of tliis line at Galería is at the height of 15,645 feet, or a little under the height of Mont Blanc, bnt it must be remembered that the cliruatic conditions are very different and more unfavorable in Peru than in Europe. Mr. E. Lane, the engineer in chief, finds that the workmen vip to an altitude of 8,000 to 10,000 feet do about the same relativo quantity of work as at rea level, provided they have been inur. .1 to the height or brought ap to Üac country. At 12,000 feet the ainount of' work deteriorates, and at 14,000 to 16,000 a full third has to be deducted from the amotint that the same man could perforan at sea level. Mules and horses are i'ound to do about the same efficiënt work proportionately as human beiiiKS ud to about 17.000 feet in the district.