126 TRINIDAD. 



by a high temperature combined with humidity, there may exist 

 in the air certain substances which, in the form of miasmatic 

 emanations, become a most material element in the development 

 of maladies, and the sanitary condition of a country. 



A warm, damp atmosphere is the condition naturally most 

 favourable to the decomposition of organic substances, either 

 animal or vegetable ; and as the gaseous exhalations evolved 

 from such decompositions are more readily held in suspension in 

 such an atmosphere, it may be considered, where suitable 

 affinities exist, as highly predisposing to very serious diseases, 

 and especially to the almost innumerable series of periodical 

 affections. 



Emanations arising from the decomposition of vegetable 

 matters are particularly noxious; and yet, when they are 

 allowed to decay in a dry air, they do not disengage any 

 deleterious principles. In order to generate those principles, 

 they must undergo the process of decay in stagnant water, 

 thus forming swamps. Swamp-water is, generally, fetid; but 

 fetidity is no positive mark of the deleterious qualities of a 

 swamp. 



Swamps or marshes are created by collections of standing 

 water, either fresh or salt ; it may be said, however, that purely 

 salt-water marshes do not exist, since they are almost invariably 

 formed by an admixture of fresh with salt-water. The latter 

 are much more dangerous than merely fresh or salt-water 

 swamps, whereas this admixture has for result to aid in the 

 decomposition of the organic matter contained in both. 



The following are the conditions necessary for the formation 

 of swamp effluvia : a damp, warm air, the ground neither too 

 dry nor too deeply covered with water. Hence the atmosphere 

 of these watery tracts always contains more or less of moisture, 

 but more during the night than the day; it also holds in 

 suspension during the former period certain substances which 

 do not seem to exist therein during the latter, so that the 

 disengagement, or at least the condensation, of marsh emana- 

 tions is less during the day, and greater at night, but particularly 

 at sunset and sunrise. Their chemical nature has not yet been 

 ascertained by analysis ; however, they have been found to 

 contain ammoniacal components, and, therefore, must be of an 

 organic or vegeto-animal nature. No doubt their mode of 



