CHAP. III. ON MOUNTAIN-SICKNESS. 43 



is marked G upon my map. This one we naturally termed the 

 Vallon de Tortorillas. The next towards the west — the Yallon 

 de Debris — leads to the glacier marked F. The third, still 

 farther to the west, was that up which our caravan had gone. 

 I called this the Vallon de Carrel. The Great Arenal stretches 

 along the base of the ridges that divide these little valleys.^ In 

 the vicinity of Tortorillas its soil is grassy, and affords pasturage 

 to sheep and cattle ; but vegetation becomes more and more 

 sparse as one proceeds towards the west, and ultimately it 

 almost entirely disappears. The soil in the centre of the plain 

 is composed of fragments of lava — much of it scoriaceous ; they 

 presently become smaller and more equal in size, and on the 

 west of the plain the surface is composed of what can only be 

 called fine sand, which drifts in this direction. This is partly 

 volcanic dust, and probably is partly derived from attrition 

 of the larger fragments. Much of the matter was no doubt 

 ejected by Ohimborazo, but it is certainly to some extent sup- 

 plemented by the volcanic dust which is constantly floating 

 about the country, and is borne by the prevalent winds towards 

 the south-west. 



This sandy soil was very loose, and toilsome to ascend even 

 upon moderate gradients. Hence I was surprised that our caravan 

 returned soon after 1 p.m., having occupied only a little more 

 than three hours in going to and returning from the second camp. 

 After allowing the animals a rest, they were reloaded with as 

 much as was good for them, and the remainder of the provisions 

 and stores were left in depot at the entrance of the Vallon de 

 Carrel. At this point I must stop to explain more particularly 

 the manner in which it was proposed to conduct our operations. 



Neither of the two Carrels, nor I myself, had ever experi- 

 enced the least symptom of mountain-sickness. None of us, 



^ These vallons cannot be seen in the view facing p. 24. They are hidden by 

 the ridge that stretches across the engraving. 



