Sarees UR eee af SS ee 
J. Orton on the Andes and Amazons. 207 
The Mississippi at St. Louis has nearly the same altitude* as 
the Amazons at the mouth of the Napo: respective distances 
from the sea, 1,400 and 2,200 miles. Below St. is the 
fall of the Mississippi is 3 in. per mile. 
Accidental variations of the barometer—These are gene- 
rally considered as reduced to nothing at the equator, - 
boldt says, the regularity of the ebb and flow of the aerial 
ocean is undisturbed by storms, hurricanes, rain and earth- 
quakes in the torrid zone of the new continent, on the coast 
and at the elevation of 13,000 ft. At Dodabetta, India, (alt. 
8,640 ft.) Lieut. Strachey found that the most violent and 
variable wind did not affect the range of the barometer, But 
in the valley of the Amazons strange irregularities have been 
hoticed in every hypsometric instrument, whether mercurial 
barometer, aneroid or boiling apparatus. No two travelers 
have noticed the same irregularity ; but all (save Azevedo and 
into), have found a lawless disturbing force. Indeed, the 
anomaly is so constant, that I am inclined to suspect the re- 
cord of the Brazilian lieutenants, because it discovers no ir- 
Tegularity, Spix and Martius gave Tabatinga the enormous 
altitude of 670 ft., and elevated Mandos 556 ft. above the sea. 
is makes the fall of the first thousand miles of the river 
five times that of the second. Castlenau found Nauta 365 ft., 
Peb , 399 ft., and Mandos 293 ft. above the sea; and com- 
Plaining that his barometer got out of order, rejected a part 
of his observations. Herndon, with a boiling apparatus, dis- 
covered to his surprise that between Nauta and Ega he was 
ascending according to th instrument, though by the river 
and his own senses he was descending. At Nauta water 
satlod at 211°-3, and at Ega at 208°-2, which would put Nauta 
aps gliding up stream though we were descending at the rate 
~ i an hour, and excepting also on the Amazons = 
.- +abatinga and Obidos. The boiling point was more 
Neowar than the height of the mercury. Our rate down the 
“po was full 40 miles a day ; and the record of the boiling 
* Mean bar. at St. Louis, 29°520; at the mouth of the Napo, 29526. 
