THE SOLAR RAYS AT GREAT ELEVATIONS. 409 



the surrounding rocks till they sometimes actually 

 splinter and crack, as if exposed to the blast of a 

 furnace, while the scanty vegetation which struggles 

 for existence at rare intervals among their sheltered 

 crevices, is that of the glacial region, whose brilliantly 

 coloured flowers grow and flourish only under the 

 dropping of water from melting snows. In the high Alps, 

 which are annually visited by ever increasing numbers 

 of our British tourists, these flowers are a never failing 

 source of wonder and delight : and many of them will 

 doubtless have remarked that the higher they climb the 

 more brilliant does the Alpine flora become. In the 

 very highly elevated regions of the Himalayas and the 

 Andes however, owing to the extreme rarefication of 

 the atmosphere, botanical and other researches become 

 a matter of serious difficulty, and indeed of danger 

 for, apart from the ordinary risks inseparable from 

 mountaineering, the stranger is here liable to severe 

 attacks of a disease known to the Spanish colonists 

 as "puna." This frequently comes on quite suddenly, 

 without any previous warning, in the form of violent 

 sickness of the stomach and vertigo, accompanied by 

 difficulty of breathing, which obliges the sufferer at 

 once to come to a standstill, and renders him in the 

 case of a serious attack incapable of further progress 

 without assistance, on account of the giddiness. 



We have suffered from these attacks in our own 

 person, and can speak feelingly as to their exceedingly 

 serious and alarming nature : as a sudden failure of the 

 heart's action, if exertion is persisted in, is liable to 

 bring the traveller's wanderings to an abrupt and per- 

 manent close. 



One such case, which had a fatal issue, we heard of 



