108 LITERATURE ON TOBBENTS, 



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at Tarbes, they have, scarcely the size of a man's heafi,; , and toTurards Mpnt- 

 de-Marson we meet almost exclusively with clay covered over with the sand 

 of the Landes, home thither probahly by the wind* 



" The day itself presents alternating colours,:, it is yellow, ochj-^ coloured, 

 or bluish ; and near Bagnferes we can in the trenches recognize some sort 

 of stone which would furbish some one or other of the colour?. By, digging 

 out blocks in all stages of disintegration, we may be said to see in actual 

 operation the manufacture of day. At some places a cutting in the ground 

 presents the appearance of mosaic work, in which granitic pebbles, perfectly 

 recognizable in their rounded forms, but softeijed by time, may be cut like 

 butter, or rather like nougat [a cake made of alnjonds and honey], each of 

 them leaving still recognizable, in spite of its decomposition, the rock from 

 which it had been torn. 



" The cone of the Gave supplies similar facts ; it is isolated on all sides ; 

 its head may be said to be in the air. The glacier which produced it 

 would meet at Lourdes, on coming out of the valley of Argelfes with a small 

 mountain of schist, which would necessitate it to divide itself; the exterior 

 branch would direct itself towards where Tarbes now stands, extending as 

 far as to Adfe ; the other branch would descend towards the position of Pan, 

 reaching as far as Saint-Pfe. Between the two branches would be turned off 

 tl^e loess ; so the summit of the glacial cone would rest on the schistose 

 mountain in the angle formed by the two branches of the glacier. At the 

 time of the retreat of the glacier aU the waters of the valley of the Argelfes 

 were united towards the west in the Saint-Pfe branch ; and the other branch, 

 that of Ad6, is still a void valley without a river — the railway from Tarbes 

 to Lourdes has been constructed there ; but this valley, devoid of a single 

 considerable water-course, is full of torrential indications. 



" The valley of Argelfes has been the subject of special study by MM. Ch. 

 Jfartins and Collomb, indefatigable explorers, who, after having dwelt on 

 the glaciers of the Alps in the Hotel mouvant des Neuchatelon, have sought, 

 from Spitzbergen to the Sahara, the traces and the causes of the glacial 

 period. These mvants thus sum up their memoir, published in Bulletin of 

 the Societe giologique de France, 2 sirie, t. xxv., p. 141, seances sur, 18th 

 November 1867, and Mimoires de I'Academie des Sciences de Momtpelier, 

 t. vii., p. 47 : — " To sum up these observations, we have ascertained in one 

 of the principal valleys of the Pyrenees — the valley of Argelfes — the 

 existence of an old glacier of the extent of 53 kilometres, which shed its 

 terminal moraines on the sub-Pyrenean undulating plain, and extended to 

 within 15 kilometres of Tarbes, with an altitude there of 400 metres, about 

 1350 feet, — its point of departure being at a mean altitude of about 3000 

 mfetres, 4000 feet, the mean slope of its surface being 1 of 0.039. 



" This glacier, including its affluents and its higher nhes, — in a word, its 

 hydrographic basin — would cover an area of about 1-400 square kilometres, 

 or 1.40' hectares. 



" The thickness of the glacier reached, at Gfedres, 850 mfetres ; at Saint- 

 Sauveur, 800 mfetres; at, Pierrefite, 675 mfetres; at Argelfes, 600 mtoes ; 

 at the Pic de Jer, near Lourdes, 412 metres. 



" The summit of the Beout, a conical mountain which rises above Lourdes 

 in the middle of the valley to the height of 792, was covered by the glacier ; 

 and evfin from the railway station of Lourdes may be seen distinctly, in 

 profile against the blue sky,,, the erratip, bowlders, scatter^ji oyer the ridge 

 of the mountain, at an elevation of 450 rofetres, 1350 feet, above the Gave. 



