and Power and Endurance. 49 



On the other hand, Mr. Perring, " rather a debilitated man, 

 and distinctly less robust than ourselves " (p. 51), escaped the 

 sickness. According to my view, the food-supply his system 

 was dealing with was not in excess of what could easily be 

 consumed by the air he breathed, even at the reduced 

 density. 



According to this view, while the artifi cial supply of oxygen 

 advocated by some investigators should be able to give relief, 

 if the oxygen could be got to its work, yet the obvious course 

 is to attack the other element ; and by a judicious preliminary 

 course of moderate starvation, combined with light work, to 

 endeavour to bring the system into the required condition of 

 reduced fuel consumption — in fact into the condition at which 

 it arrived in Mr. Whymper's case, through the painful path 

 of the attack of mountain-sickness. 



So far I have spoken of what may be called " great-alti- 

 tude " mountain-sickness. As to the more ordinary form, I 

 am sorry to say I was at one time a sufferer. Experience 

 enabled me to overcome it by adopting a slow uniform mea- 

 sured pace. But, after the disappearance of the agility of 

 youth, for some seasons I always suffered in my first expedi- 

 tions, even at quite moderate elevations. And I have no 

 doubt whatever that it was due to the system being over- 

 tasked ; that is to say, when I was endeavouring to do some- 

 thing like, say, ^ of a horse-power for a time far longer 

 than I was capable of, I collapsed, probably not being capable 

 of doing more than, say, -£$ of a horse-power for any con- 

 siderable time, at all events when out of training. 



So far I have avoided going into numerical details, as they 

 are not necessary for the general explanation, and they open 

 up an exceedingly wide subject. But I propose now to deal 

 shortly with certain relations of the external work which can 

 be performed by men ; this is conveniently reckoned in terms 

 of " horse-power/' 



One "horse-power" is commonly denned as 550 footpounds 

 per second, without qualification. When recently horses were 

 replaced by electric motors on certain tramways, it was gene- 

 rally considered a surprise that motors of about 35 H.P., as 

 above defined, were required to replace the horses. The 

 explanation is that the 550 footpounds per second definition 

 was based on the average effort that horses could exert for a 

 considerable time. The output of power of a horse on such 

 occas : ons as drawing a load up a sharp hill must be quite ten 

 times a nominal horse-power. And the machine is required 

 to be able to replace the greatest effort of which, say, 3 horses 

 are capable. 



Phil. Mag. S. 5. Vol. 35. No. 212. Jan. 1893. E 



