12fi Prof. T. G. Bonney. On the [June 19, 



terminates. Its lower slopes extend a long distance into the basin of 

 Riobamba, and die out only a few miles to the west of the town of 

 that name." 



[ From the Arenal Mr. Whymper has sent to me four small parcels 

 of the " sandy " material. The first is a number of fragments of lava, 

 slightly scoriaceous, varying in colour from a pale to a warm grey 

 and speckled with black crystals (probably augite), the largest being 

 about 1 inch in diameter. Small crystals of felspar appear to be 

 rather abundant, and fragments of this and other minerals are rather 

 frequent in the dust which is mixed up with the coarser parts. 

 Another parcel consists chiefly of rather small lapilli, some being of a 

 pale reddish-brown colour. A third consists of lapilli of the above 

 tint, varying in size from rather larger than a hemp seed to a little 

 less than a mustard seed; and the fourth, like the first, consists of 

 larger fragments mingled with a considerable amount of fine dust, the 

 whole being a little paler in colour than the first specimen. I have 

 not thought it necessary to subject these to a minute examination, as 

 I have no doubt that they have a general agreement in their 

 composition with the rocks of the mountain, and are simply volcanic 

 dust and lapilli, which have been ejected from Chimborazo in the 

 days when it was an active volcano, and are now a good deal decomposed 

 by the action of percolating water. T. G. B.] 



" In plan, Chimborazo is elliptical, and its longer diameter extends 

 approximately from north-east to south-west. In this direction, at 

 the level of 14,000 feet, the mountain extends over about 14 English 

 miles. When viewed from certain directions Chimborazo is seen to 

 be crowned by two rounded snow-covered points. From true east or 

 west these points conceal each other, and the general appearance of 

 tlie mountain when viewed at considerable distances from all points of 

 the compass, is that of a cone, the minor details being indistinguishable. 



" On a close approach, the subordinate features destroy the cone- 

 like effect of Chimborazo. From the south, the two summits are well 

 seen, but as the traveller bound for Quito passes round the eastern 

 side the mountain gradually takes the appearance of a range. From 

 the north-west or north-north-west, at a distance of three or four 

 miles from the mountain, the lofty and almost vertical cliffs which are 

 found on that direction assume great importance, and nearly conceal 

 the snowy domes which crown the true summit. 



" The ridges which radiate from the upper part of Chimborazo are 

 too numerous to be specified. Those not covered by snow or glacier 

 are mostly, if not entirely, old flows of lava, which have been greatly 

 eroded, and are much decomposed. In numerous places they are 

 almost completely buried in their own ruin. The general appearance 

 of the ridges which are enveloped by snow or glacier renders it 

 probable that they too are fundamentally old lava streams. 



