THE BOILING POINT. 



257 



that they abandoned their families ; but in my judgment this was a benefit 

 to them, rather than an injury, for the man at home is, in a great 

 measure, supported by the woman. 



I could not make an estimate of the number of Peruvian Indians in 

 Brazil ; but I noticed that most of the tapuioa were Cocamas and 

 Cocamillas, from the upper Amazon. 



We entered the Amazon at 4 p. m. The mouth of the Teffe is three 

 hundred yards wide, and has thirty feet of depth and one mile per hour 

 of current. This is an inconsiderable stream, and may be ascended by 

 canoes to near its sources in twenty days. In ten or twelve days' ascent, 

 a branch called the Rio Gancho is reached, which communicates by a 

 portage with the Jurud. Indians of the Purus, also, sometimes descend 

 the Teffe to Egas. 



I was surprised to find the temperature of boiling water at Egas to 

 be but 208°.2, the same within .2 of a degree that it was at a point 

 one day's journey below Tingo Maria, which village is several hundred 

 miles above the last rapids of the Huallaga river ; at Sta. Cruz, two days 

 above the mouth of the Huallaga, it was 211°.2; at Nauta, three 

 hundred and five miles below this, it was 211°.3 ; at Pebas, one hundred 

 and seventy miles below Nauta, 211°.l. I was so much surprised at 

 these results that I had put the apparatus away, thinking that its indi- 

 cations were valueless ; but I was still more surprised, upon making the 

 experiment at Egas, to find that the temperature of the boiling water 

 had fallen three degrees below what it was at Sta. Cruz, thus giving to 

 Egas an altitude of fifteen hundred feet above that village, which is 

 situated more than a thousand miles up stream of it. I continued my 

 observations from Egas downwards, and found a regular increase in the 

 temperature of the boiling water until our arrival at Para, where it 

 was 211°.5. 



M. Castelnau gives the height of Nauta at four hundred and five feet 

 above the level of the sea ; the temperature of boiling water gives it at 

 three hundred and fifty-six. Both these, I think, are in error ; for, taking 

 off forty feet for the height of the hill on which Nauta is situated, we have 

 three hundred and sixty-five for the height of the river at that point 

 above the level of the sea. Now, that point I estimate at two thousand 

 three hundred and twenty -five miles from the sea, which would give the 

 river only a fall of about sixteen-hundredths of a foot per mile — a de- 

 scent which would scarcely give the river its average velocity of two 

 and a half miles per hour. 



From an after-investigation, I am led to believe that the cause of this 

 phenomenon arises from the fact that the trade-winds are dammed 

 17 



