388 Barometric Anomalies about the Andes. 
pheric pressure at the sea level. In other words, this traveller 
found himself under a ridge or-mountain of atmosphere, the pres- 
sure of which away up on the side of the Andes was nearly as 
great as is the mean pressure of the atmosphere down upon the 
sea shore. 
Drifting along down the river from Nauta, Lieut. Herndon, 
much to his surprise, found that according to his boiling point, 
he was ascending or going up-hill quite rapidly, though by t 
river and his own senses, he was descending. Finally, by his 
boiling point, at Egas, he ceased to ascend, and again began to _ 
descend according to it and his own senses also. 
It is worthy of remark, that M. Castlenau, the French traveller, 
who preceded Herndon, observed the same phenomenon with re- 
gard to the high barometer, at Nauta, that the American did with 
regard to the boiling point. - 
Their measurements, which were both made on a bluff or high 
bank of the river, differ from each other as to the height above 
the sea level, 51 feet. At the next place—Pehas—where they 
both again observed, the difference between them is 138 feet. - 
ellers, Spix and Martius, observed. hese observations give the 
height of Barra, by Castlenau, 293 feet ; by Herndon, 1,380; by 
Spix and Martius, 522 feet; above the level of the sea. M. Cas- 
tlenau complains that in his descent of the Amazon his barometer 
got out of order, and that in consequence, he was compelled to 
reject a portion of his observations. Was it because his baro- 
meter made him apparently go zp hill, as Herndon’s boiling peimt 
did, when he knew he was goiug down stream? 
It is to be hoped, if this should ever*meet the eye of that clever 
French traveller, he will have the goodness to let the world see 
those rejected observations. 
Moreover, it would probably depend upon the season of the 
year whether barometrical observations along the Amazon, and to 
the north of it, would detect this supposed repetition of the An 
in the air. When the equatorial calms are upon the Amazon, as 
fora month or two annually they are, the trade winds do not 
blow at Nauta or Pebas, consequently there would be no accumu- 
lation of air then, and from this eause, over those places. But at 
the other season, when the S. E. trades are felt at Pebas a 
Nanta, and when they are impinging and pressing against the 
ndes, I imagine they accumulate and pile up too, and will make 
the barometer feel the weight of this accumulation. Now, the 
fact that those travellers passed along the Amazon at differrent 
seasons of the year, may help to account for this extraordinary 
difference in thei trical observations. . 
- Reasoning from these facts and conjectures, I have been led to 
ask the question—that if there be an elevation in the atmosphere 
