1899.] on Climbs and Explorations in the Andes. 191 



culminating points was climbed. It was ascended and thoroughly 

 explored by the FitzGerald expedition in 1897. The only observa- 

 tions of any original importance there made by my expedition 

 were in respect to a peculiar formation of snow locally known as 

 Nievcs Penitentes. Nieves Penitentes are named from a supposed 

 resemblance to a crowd of white-robed penitents. They are an 

 assemblage of cones of snow, or rather they would better be de- 

 scribed as a field of snow whose surface consists of a multitude of 

 cones in close proximity to one another, and varying in height from 

 a few inches to a few feet, though at any moment the cones near 

 together will probably all be of about the same height. It has been 

 usual to ascribe the formation of this many-coned surface to the 

 action of violent winds, which are conceived of as causing the snow 

 to eddy and whisk about and thus build itself up into these peculiar 

 spires. Such, however, in my opinion, is not the true explanation. 

 To begin with, if winds were the cause, this conical formation of 

 snow surface should be found in windy places such as Greenland and 

 Spitsbergen, where, on the contrary, this form of surface is unknown. 

 It has never been noticed in the Alps or the Caucasus, nor, as far as 

 I know, in the northern regions of the Himalayas, but it is found in 

 Mexico and in other parts of the Andes. The cones at the beginning 

 of the warm season are very small ; as the year advances they in- 

 crease in size, by the deepening of the hollows between them, till 

 they become eight feet or more in height. They are, in fact, 

 formed by some process of melting, not by any process of building 

 up. They never consist of new snow. A careful examination of 

 them at many points about Aconcagua revealed the fact that they 

 are not of circular but elliptical section, and that they do not 

 stand vertically, but bend over towards the north. The major axis of 

 the ellipse was in every case more or less east and west, sometimes 

 with one end or the other brought around somewhat to the north in 

 cases where the site was sheltered by some neighbouring eminence 

 either from the morning or evening sun. A field of newly fallen 

 snow may be regarded as having a fiat surface, but the accidents of 

 its structure will in process of melting soon cause inequalities to 

 arise. These inequalities naturally take the form of pits and lumps, 

 and when the sun is very nearly vertical at mid-day, it naturally pro- 

 duces more melting in the bottoms of the hollows than it does on the 

 slopes leading down to them. These hollows once formed tend to 

 deepen by melting, and the deeper they become, and the steeper the 

 sides, so much the more does the deepening tendency increase. The 

 originally round summits are sharpened by a similar process. The 

 sun, always remaining to the north of the zenith at mid-day, causes 

 the hollows to have a northward tilt. When the hollows have been 

 so deepened and widened that they ultimately run into one another, 

 there remains standing between them a series of cones, and these are 

 the Nieves Penitentes of the Andes. Sometimes, where the snow bed 

 is only a few feet deep, the hollows will be melted down to the sur- 



