WESTERN COAST OF S. AMERICA. 69 



to alterations not indicated by the thermometer, and 

 depending solely on the humidity and dryness of 

 the atmosphere. 



The third division, extending a distance of nearly 

 1700 miles from Payta to the entrance of the Gulf of 

 California, forms a perfect contrast with the second. 

 All this humid and burning coast has alternate wet 

 and dry seasons, and is clothed in the most luxuriant 

 vegetation, which approaches to the water's edge. 

 The mean temperature may be called 82°. Man- 

 groves, avicennias, and other shrubs, flourish abund- 

 antly along these swampy shores ; and their inter- 

 twining roots form retreats for moUuscae, and an in- 

 finite variety of shell-fish and insects. Places of this 

 kind are invariably deleterious to the human con- 

 stitution. The heat and humidity of the air increase 

 the developement of diseases in two different man- 

 ners—by increasing the irritability of the organs, and 

 by the production of miasmata. 



The disease which we chiefly encountered in this 

 track was an ardent fever, resembling in every re- 

 spect the yellow-fever of the West Indies, both in 

 the suddenness of its attack, and the violence of its 

 symptoms. It yielded to precisely the same treat- 

 ment, by copious and properly regulated bleeding. 



