Climate on tpib Aiviazon. 285 



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the abundance and beauty of animal forms, increases from 

 the Atlantic to the Andes. At the foot of the Andes, Poep- 

 pig found that the most refined sugar in a few days dissolved 

 into sirup, and the best gunpowder became liquid even when 

 inclosed in canisters. So we found the Napo steaming with 

 vapor. Fogs, however, are rarely seen on the Amazon. 



The animals and plants are not all simultaneously affect- 

 ed by the change of seasons. The trees retain their verd- 

 ure through the dry verao, and have no set time for re- 

 newing their foliage. There are a few trees, like Mongru- 

 ba, which drop their leaves at particular seasons ; but they 

 are so few in number they create the impression of a few 

 dead leaves in a thick-gromng forest. Leaves are falling 

 and flowers drooping all the year round. Each species, 

 and, in some cases, each individual, has its own particular 

 autumn and spring. There is no hibernation nor aestiva- 

 tion (except by land shells); birds have not one uniform 

 time for nidification ; and moulting extends from Februa- 

 ry to May. 



Amazonia, though equatorially situated, has a temperate 

 climate. It is cooler than Guinea or Guiana. This is ow- 

 ing to the constant evaporation from so much submerged 

 land, and the ceaseless trade winds. The mean annual 

 temperature of the air is about 81°.* The nights are al- 

 ways cool. There are no sudden changes, and no fiery 

 " dog days." Venereal and cutaneous affections are found 

 among the people ; but they spring from an irregular life. 

 A traveler on the slow black tributaries may take the ter- 

 tiana, but only after weeks of exposure. Yellow fever and 

 cholera seldom ascend the river above Para ; and on the 

 Middle Amazon there are neither endemics nor epidemics, 



* Agassiz calls the average temperature 84°, which, it seems to us, is too 

 high. The mean between the temperatures of Para, Manaos, and Tabatinga 

 is 80.7° 



