1851.] 
HEIGHT ABOVE THE SEA. 
245 
At Tomo I had observed signs of stratified upheaved 
rocks close to the village. Here the flat granite pave- 
ment presented a curious appearance : it contained, 
imbedded in it, fragments of rock, of an angular shape, 
of sandstone crystallized and stratified, and of quartz. 
Up to Sao Carlos I had constantly registered the boiling- 
point of water with an accurate thermometer, made for 
the purpose, in order to ascertain the height above the 
level of the sea. There I had unfortunately broken 
it, before arriving at this most interesting point, the 
watershed between the Amazon and the Orinooko. I 
am however inclined to think that the height given by 
Humboldt for Sao Carlos is too great. He himself says 
it is doubtful, as his barometer had got an air-bubble in 
it, and was emptied and refilled by him, and before re- 
turning to the coast was broken, so as to render a com- 
parison of its indications impossible. Under these cir- 
cumstances, I think little weight can be attached to 
the observations. He gives, however, 812 feet as the 
height of Sao Carlos above the sea. My observations 
made a difference of 0*5° of Uahrenheit in the tempera- 
ture of boiling water between Barra and Sao Carlos, 
which would give a height of 250 feet, to which may be 
added fifty feet for the height of the station at which 
the observations were made at Barra, making 300 feet. 
Now the height of Barra above the sea I cannot con- 
sider to be more than a hundred feet, for both my own 
observations and those of Mr. Spruce with the aneroid 
would make Barra lower than Para, if the difference of 
pressure of the atmosphere was solely owing to height, 
the barometer appearing to stand regularly higher at 
