80 A NATURALIST IN MEXICO. 



on. The guides were now some distance ahead, and we 

 followed on as quickly as possible. Soon the snow-field 

 was reached, and here the truly difficult part of the ascent 

 began. The field was cut up into little hillocks, which 

 rendered progression over it much easier than it would have 

 been, had it been a smooth fiald of frozen snow. When 

 within three hundred feet of the summit, I was ssized with 

 the most violent symptoms. My head swam, my eyes be- 

 came bloodshot, and my stomach felt very qualmish. A 

 ringing noise entered my ears, and I was obliged to desist 

 from ascending further. Another of my companions was 

 affected in the same manner, and but one was able to reach 

 the actual summit, and he had to be hauled up with ropes 

 by the natives. Our descent was somewhat novel. A na- 

 tive had carried with him a piece of straw matting, and upon 

 this we sat and were pulled down a sandy incline of thirty- 

 five degrees, in much the same manner that coasting is done 

 in Canada. We arrived at the camp foot-sore and weary, 

 and were glad enough to lie down and rest. 



Our determination showed that the height formerly 

 given for the mountain is too low. - After making allow- 

 ances for slight variations, the height of the mountain is 

 18,200 feet. The barometer, at the summit, read 15.56 

 inches, and the temperature was 35*^ Fahr. During the as- 

 cent of the second day, the barometer indicated a drop of .1 

 inch. In 1796, Ferrer, by means of angle measurements 

 taken from the Encero, determined the height to be 17,879 

 feet. Humboldt, a few years later, measured the mountain 

 from a plain, near the town of Jalapa, and obtained 17,375 

 feet. He observed, however, that his angles of elevation 

 were very small, and the base-line difficult to level. In 

 1877, a Mexican scientific commission, composed of MM. 

 Plowes, Rodriguez, and ^'igil, made the ascent of the 

 volcano from the side of San Andres, and determined the 



