212 Historical 



blood-vessels, and the increased difficulty of the passage of the 

 blood through the lungs. We shall return, in. the next chapter, to 

 the value of these theories which it would be premature to discuss 

 at present. 



According to the account of Haller, we see that travellers in 

 the Alps had already experienced painful effects of the decrease 

 of barometric pressure. However, no explorers had yet trodden 

 the summits of any of the giants of the Alps, Mont Blanc, Monte 

 Rosa, nor the Jungfrau, which rise to an elevation of more than 

 4000 meters. Below this level, even slight symptoms are rather 

 rare. The Genevan physicist de Luc 21 is surprised at that, when 

 he considers the great decrease in the weight of the air supported 

 by the body; he draws from it a very reasonable conclusion about 

 the effect on the health which certain physicians attribute to baro- 

 metric changes: 



We were very comfortable near the little rocks to which we had 

 descended (the Buet glacier, barometer 19 inches, 6 lines; 9355 feet 

 above sea level) . . . We were surprised that we perceived the dif- 

 ference in the density of the air only through our instruments, that no 

 discomfort or disagreeable sensation warned us that the air we were 

 breathing was nearly a third less dense than that of the plain, that 

 the weight of the atmosphere upon our bodies was one hundred quin- 

 tals less without any disturbance of the inner equilibrium. What a 

 marvelous machine this is, which adapts itself to such great variations 

 in the very causes of its principal movements, without their ceasing to 

 be regular! 



I cannot refrain from saying in this regard how much mistaken 

 certain doctors were who attributed to the difference in the weight 

 or the density of the air the changes experienced by certain persons 

 when the barometer falls, and who undertook to explain them by the 

 lack of equilibrium between the inner and the outer air, or by the 

 effect which a more or less dense air can produce upon the movements 

 of the heart and the lungs. 



If these variations had a perceptible effect upon our organs, what 

 would become of those chamois hunters who pass every day from the 

 depths of the valleys to the summits of mountains equally high . . . 

 Even asthmatic persons are not affected by them; at least I was on the 

 mountain of Saleve with one of my friends who feared this effect and 

 did not experience it. (P. 328.) 



We have seen that Canon Bourrit, in his ascent of Buet, was 

 less fortunate than de Luc; the accounts of de Saussure and Pictet 

 show, moreover, that this mountain, in spite of its moderate height, 

 is one of those on which travellers are most easily affected in the 

 ascent. In this connection, Bourrit - 2 makes a strange remark about 

 the difference in density, at an equal altitude, between the air of 



