In the mountainous regions of the interior, nature presents difficulties which, though of a different description, are equally as appalling as those experienced on the coast. The sheds erected at _pascanas_ (or halting places) in the vast unpeopled tracts of the bleak mountain districts, and on the table lands, were inadequate to afford shelter to more than a small number, so that the greater part of the troops were obliged to bivouac sometimes in places where the thermometer falls _every night_ considerably below the freezing point, and this _throughout the year_; whereas it often rises at noon, in the same place, to 90 degrees. It may be readily imagined what must have been the sufferings of men, born in, or accustomed to, the sultry temperature of Truxillo, Guayaquil, Panama, or Cartagena. The difficulty of respiration, called in some places _la puna_, and in others _el siroche_, experienced in those parts of the Andes which most abound in metals, was so great at times, that, whilst on the march, whole battalions would sink down, as if by magic, and it would have been inflicting death to have attempted to oblige them to proceed until they had rested and recovered themselves. In many cases life was solely preserved by opening the temporal artery. This sudden difficulty of respiration is supposed to be caused by occasional exhalations of metalliferous vapour, which, being inhaled into the lungs, causes a strong feeling of suffocation. During certain months of the year, tremendous hail-storms occur. They have fallen with such violence that the army has been obliged to halt, and the men being compelled to hold up their knapsacks to protect their faces, have had their hands so severely bruised and cut by large hail-stones as to bleed copiously. Thunder-storms are also particularly severe in the elevated regions. The electric fluid is seen to fall around, in a manner unknown in other parts of the world, and frequently causes loss of life. Such storms have often burst at some distance below their feet, as the army climbed the lofty ridges of the Andes. The distressing fatigues of the most difficult marches in Europe cannot perhaps be compared to those which the patriot soldiers underwent in the campaign of 1824. From Caxamarca (memorable for the seizure and death of Atuhualpa) to Cuzco, the whole line of the road (with the exception of the plain between Pasco and the vicinity of Tarma, twenty leagues in extent, and the valley of Xauxa) presents a continuation of rugged and fatiguing ascents and declivities. That these difficulties do not diminish between Cuzco and Potosi may be inferred from the following fact:--