INTRODUCTION. vii 



that others are liable to bleeding at the nose, or habitually suffer 

 from headache, and that this accounts for much which has been 

 laid to rarefaction of the air ; and further, it is said, or conjectured, 

 that the fatigues inseparable from travel in mountain-regions 

 account for more : in short, that mountain-sickness is to be attri- 

 buted to the frailties of human nature, or to the imperfections of 

 individual constitutions, and is considered as a sign, or indication, 

 of weakness or incompetency. 



It is undeniable that there is some truth in these observations, 

 and it can scarcely be doubted that effects which have been pro- 

 duced by fatigue have often, wrongly, been attributed to rare- 

 faction of the air, and that effects which have been produced by 

 rarefaction of the air have often been assigned to fatigue. The 

 immunity from unpleasant symptoms which has sometimes been 

 enjoyed by aeronauts, even when bounding in a few minutes to 

 enormous elevations,^ has tended to foster scepticism ; and has 

 appeared to support the opinion that fatigue and personal imper- 

 fections have had much to do with mountain-sickness, and not to 

 accord with the view that it is produced by diminished pressure — 

 otherwise, why should these persons, transported without effort to 

 superior elevations in the air, have escaped, whilst others, at much 

 inferior ones upon the earth, suffer ? 



It is scarcely necessary to occupy these pages with a mass of 



^ The following data are taken from the Reports of Mr. J. Glaisher, F.R.S., to the 

 British Association for the Advancement of Science, 1862-3 — 



Diff. of Time. Diff. of Pressure. 

 44 min. 14-55 inches. 



33 „ 14-62 



32 ,, 14-85 „ 



Starting from the level of the sea, the height attained in each case was about 19,000 

 feet, without injurious effects being felt. I am not aware that any one, upon the 

 earth, has ever experienced a natural difference of pressure of fourteen and a half 

 inches in less than four or five days. 



Date. 

 July 17, 1862 



Time. 

 9.43 a.m. 

 10.27 „ 



Barometer. 

 29-193 

 14-637 ■ 



Sept. 5, ,, 



5> 5? 



1.3 P.M. 



1.36 „ 



29-17 ) 

 14-55 S 



April 18, ,, 



1.17 „ 

 1.49 „ 



29-66 / 

 14-81 S 



