' . in relation to Disease. 45 



These observations lessen any suq)rise at the great power of 

 accommodation by habit to a constant high degree of rarefied 

 atmosphere. The city of Mexico stands 7,460 feet above the 

 level of the sea ; and there are inhabited points in the Andes 

 of Peru even 6,000 feet still higher.* It must be admitted, 

 however, that we have no sufficient knowledge of the diseases 

 in these localities, or of the average rate of mortality, to jus- 

 tify inferences as to effects on the body derived from this single 

 physical cause, when forming what may be termed a constant 

 condition of climate. 



On a general view of the circumstances stated, there is rea- 

 son to conclude that the influence of the different degrees of 

 atmospheric pressure in disturbing the bodily functions and 

 general health, is rather derived from the frequency of fluc- 

 tuations, than from any state long continued, either above or 

 below the average standard ; — that, of the two conditions, sud- 

 denly incurred in any extreme degree, the human frame is bet- 

 ter capable of withstanding a rarefied than a condensed at- 

 mosphere ; — and that, in every case, the previous health, and 

 proneness to disorder in particular organs, are greatly concerned 

 in determining the results on the body. 



4. Electricity/ of the Atmosphere. — Little though its influence 

 has yet been defined, I believe that the electrical state of the 

 atmosphere is that of all its conditions which has most im- 

 portant and diffused effects on the animal economy ; more rapid 

 and pervading than any other ; and, as one of the vital stimuli, 

 more intimately allied to the functions of the nervous system. 

 It is that, further, which most closely blends itself, either as 

 cause or effect, with all other meteorological changes ; produc- 

 ing thereby many of the difficulties already noticed in estimat- 

 ing then- relative amount of influence. When modern science 

 has shewn us that every chemical action is attended by, if not 

 identical with, electrical change ; — that the processes of vege- 



The fii'st 11,000 feet were passed through in about seven minutes. Yet, 

 under these remarkable circumstances, Mr Rush suffered no inconvenience 

 but from cold ; and Mr Green little other than from the toil of discharging 

 ballast and gas at different intervals, which huiried the respiration during 

 the time. 



* Mr Pentland, in 1826, ascertained the height of the town of Potosi to be 

 13,260 feet above the Pacific. Humboldt mentions inhabited places on the 

 Cordilleras at equal elevation. 



