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Show 278 'l'IERRA DEL FUEGO. June, 1834. In considering this table, and beginning from the south, we observe, that through the first twelve degrees, the height of the snow-line rises only a little more than 2000 feet. In this space the climate and productions of the country are in many respects very uniform . . In the succeeding nine degrees the rise is no less than nine thousand feet. Before any one pronounces this to be impossible, let him reflect well that the height of the snow-line very much depends on the heat of summer. In Chiloe no fruit, excepting apples and strawberries, comes to perfection; it is even oftentimes necessary to carry the barley and corn into the houses to be ripened:* on the other hand, in central Chile, even the sugar-cane t has been cultivated out of doors, and during a long summer of seven months the sky is seldom clouded, and rain never falls. The island of Chiloe, as well as the neighbouring main-treme variation. I was told, that during one remarkably dry and long s~Immer, all the snow disappeared from Aconcagua. Not being at the t1me aware of the extraordinary elevation of this mountain (23,000), I did not closely cross-question my informers. It must be remembered that even in ordinary summers the sky is generally cloudless for six or seven months, that no fresh snow falls, and that the atmosphere is excessively dry .. ~t may be asked whether vast quantities of snow would not, under this cond1t10n of circumstances, be evaporated? so that it miaht be possible that all t~e sn.ow should disappear from a mountain withou~ the temperature havmg nsen above the freezing point. Mr. Miers (vol. i., p. 384) ~~ys he passed the Cordillera by the Cumbre Pass on May 30th, 1819, when not the smallest vestige of snow was observable in any part of the An.des.". Yet Aconcagua is in full view in the approach to this pass. Mr. Miers, m another part (p. 383), makes a general assertion to the same effect. § See Mr. Pentland's most interesting paper in the Geograph. Journal, read March 1835. II Journal of Geograph. Soc., vol. i., p. 165. . '* Fo.r thi~ fact I may quote, as additional authority, Aguerros Descripcwn H1stor1al de la Provincia de Chiloe, 1791, p. 94. i· ~iers's Chile, vol. i., p. 415. It is said that the sugar-cane grew at Ingemo, lat. 32°-33°, but not in sufficient quantity to make the manufacture profitable. In the valley of Quillota, south of Ingenio, I saw some large date palm-trees. June, 1834. ' GLACIERS. 279 ~11$' la~d, is concealed by one dense forest, dripping with moisture, and abounding with ferns and other plants that love a humid atmosphere: while the soil of central Chile, where not irrigated, is arid and nearly desert. These two countries, so remarkably opposed to each other in every character, blend together rather suddenly near Concepcion, in lat. 37°· I do not doubt, the plain of perpetual snow undergoes an extraordinary flexure in the district where the forest ceases; for trees indicate a rainy climate, and hence a clouded state of atmosphere.* From central Chile to Bolivia, a space of 16°, the rise of the snow-line is only 2000 feet. If Bolivia possessed an atmosphere as clear as that of Chile, the limit in all probability would be even higher than the present 17,000. The cause why the limit in the equatorial regions should be lower than in a latitude seventeen degrees to the southward, I leave to those to explain, who have more means of information respecting the dryness and clouded state of the atmo-sphere in the respective regions. . The presence of glaciers depends on the accumulatiOn of a large mass of snow, subject to some variations of ~emperature, sufficient partially to thaw, and then reconsolidate the * The average degree of atmospheric transparency seems to be ~ most important element in determining the climate of any place. Dr. Richardson (Report to Brit. Assoc. for 1836, p. 131) has remarked that Pr?fessor Leslie, from experimenting on the effects of r~diation only in an msular climate deduced theoretical inferences respectmg the mean temperature of the ~ear, extremely different from the results obtained un.der t?e clear atmosphere of the polar regions. I apprehend central Clul: will bear comparison with any part of the world for the clearness of Its sky, and Chiloe for one of an opposite condition.: therefore we should not feel surpris~d, if the effects of two such opposite ~limates at first a~pear and malous. The remarkable difference in the height of the snow-hue, on the opposite sides of the Himmalaya, has hee.n ex~lained by Humb~ldt and Jacquemont, on the same principle : and m a hke manner, the d1fference between the heights on the Pyrenees and on Caucas~s, the latter mountains being characterized by a climate more excessive, than that of the former. |