92 THE ISTHMUS OF PANAMA, 



see but little, nor could I hear from reliable sources 

 of their existence to any great extent, unless it was 

 perhaps at Chagres. With the exception of one 

 season, there has never been any cholera, and then 

 but few cases occurred, and they were confined to 

 Chagres and Gorgona ; and yellow fever has never 

 yet been known, at least so I was informed, and I 

 never learned to the contrary. A severe form of re- 

 mittent or bilious fever prevails to a considerable 

 extent, sometimes, and there are occasional cases of 

 a bad form of congestive fever, but they are usually, 

 if not always, the result of great exposure, or intem- 

 perance. 



Almost every one who visits the Isthmus to re- 

 main there any considerable length of time must ex- 

 pect, as a matter of course, to be more or less af- 

 fected by the climate, yet not necessarily to have 

 fever. They will be predisposed to it by the miasma, 

 but whether or not they will have it will depend, of- 

 tentimes, upon an exciting cause. 



By observing proper precautions, a great deal 

 may be done to avoid the miasma, which is the es- 

 sential cause of the fevers. Miasma is eliminated 

 while the surface is drying, after having been satu- 

 rated by an overflow of the streams or previous rains ; 

 consequently, at such times the atmosphere contains 

 more poison than any other. Another fact which has 

 long been observed is, that the evening or night air 

 is most of all pernicious, not so much because it is 

 cool or damp, but from the unhealthy exhalations 

 which hover near the earth like smoke and fog, dur- 



