176 



NA TURE 



[December 25, 1902 



Darwin's time, they actually ended in the water, now 

 they are cut off from the channel by belts of densely 

 wooded moraine. The former greater extension of the 

 ice is also shown by the way in which "the graceful ice- 

 rounded foundation rocks of this and all the othei 

 mountains around slope up to the cliff and jagged arretes 

 above" (p. 199), and proofs of oscillations of level are seen 

 in the raised beaches and iceberg-carried boulders near 

 Otway Water (p. 219). 



Aconcagua (pp. 71, 72) towers into the sky, the 

 grandest peak of the southern Andes. It appears to be 

 built up of approximately horizontal beds of volcanic 

 rock of different texture, hardness and friability, which 

 are carved into steps like those which gave their name to 

 the "trap" rocks of Sweden. The steps are better pre- 

 served towards the right- and left-hand sides of the slope 

 than in the middle, where the downward drift of debris and 

 the fall of avalanches are most common. The edges of the 

 steps are there com- 

 pletely worn away 

 and buried. The flow 

 of debris down the 

 face is such that the 

 fragments tend to 

 become rounded or 

 subangular, like peb- 

 bles in a brook by 

 their friction against 

 one another. When 

 he was descending 

 the mountain, the 

 stones at one point 

 (about 20,500 feet 

 up) poured away be- 

 neath his feet and 

 disclosed the sub- 

 jacent rock, which 

 he perceived to be 

 ground quite smooth 

 by the passage of the 

 debris over it. 



Sir Martin gave 

 some time to the 

 examination of those 

 curious remnants of 

 great slipped or 

 drifted masses of 

 snow, the nieves 

 penitentes, so ca'led 

 because they stand 

 like devotees enve- 

 loped in shroud-like 

 robes doing penance. 

 They require peculiar 

 conditions for their 

 full development, and therefore, although somewhat similar 

 pillar-like remnants of melting snow may sometimes be 

 seen even in this country, they are not common anywhere 

 in the Old World and only over limited areas in South 

 America. They are cut out of avalanche snow which has 

 been subjected to pressures roughly perpendicular to the 

 direction of its fall, and thus hardened into approximately 

 vertical strata of different densities. The wind has 

 nothing to do with their origin, but they are carved out 

 by the melting action of direct solar radiation. They are 

 roughly elliptical and somewhat bent over to the north, 

 the major axis of the elliptic sections being oriented east 

 and west. On searching for penitentes in different 

 stages of development, he found that a thick bed of well- 

 compacted snow, when exposed to the action of the 

 sun, soon becomes pitted over with little saucer-like de- 

 pressions, and the deeper these become, the less power 

 has the sun's rays upon their sides and the more upon 

 the bottoms of the depressions. The hollows enlarging 



ultimately run into one another, leaving rough pyramids 

 of snow standing up between them, until at last the ground 

 is reached ; the spires are entirely separated from one 

 another and are seen standing about on the stony floor 

 like separate sugar cones. 



There is also a mountain called Penitentes (p. 10S), 

 from the weathered-out columnar structure of the rocks 

 which form its summit, not unlike what we sometimes 

 see in our strongly jointed Mountain Limestone or Mill- 

 stone Grit. 



Many other curious questions arise out of an examin- 

 ation of such an area ; for instance, the great uncon- 

 formity (p. 105) ; the inosculating valleys (pp. 127, 131) ; 

 the landslips and rock creep, or rivers of mud and stone, 

 similar to those described by Heim in Switzerland ; the 

 moraines modified by blown sand (pp. 55, 56). 



So little has been done towards the exploration of 

 those strangely varied and, for most people, inaccessible 



Fig. 2. — Nieves Penitentes ; the last stage. (From Conway's " Aconcagua and Tierra del Fuego.") 



regions that we gladly welcome Sir Martin Conway's 

 diary of his adventurous journey through southern Chili 

 and Tierra del Fuega, and of his difficult climb and 

 almost equally dangerous descent of Aconcagua and 

 Sarmiento. T. McK. H. 



SECONDARY AND TECHNICAL EDUCATION. 



NOW that the Education Act has become law, one of 

 the first duties of the newly constituted local 

 authorities will be to determine what are the educational 

 needs of their districts and how far these needs are met 

 by existing institutions ; they will then be able to decide 

 in what directions increased educational facilities are 

 needed and how they can most efficiently provide what 

 is wanted. 



It is in the domain of secondary education that such 

 a survey as is foreshadowed above is likely to form most 



NO. I730, VOL. 67] 



