292 ON THE ORIGIN AND HISTORY 



have seldom more than a foot of soil to cover the coral rock, 

 and are therefore under the drying process of a tropical sun, 

 brought almost immediately after the rains into a state to give 

 out pestilential miasmata. 



I shall conclude this paper with a few more observations on 

 some of the qualities not yet noticed of the marsh poison. 

 No experiments hitherto made have enabled us to pronounce 

 whether it be specifically heavier or lighter than common air ; 

 but it evidently possesses an uncommon and singular attrac- 

 tion for the earth's surface ; for in all malarious seasons and 

 countries, the inhabitants of ground floors are uniformly affect- 

 ed in a greater proportion than those of the upper storeys. 

 According to official returns during the last sickly season at 

 Barbadoes, the proportion of those taken ill with fever, in the 

 lower apartments of the barracks, exceeded that of the upper 

 by one-third, throughout the whole course of the epidemic. 

 At the same time it was observed, that the deep ditches of the 

 forts, even though they contained no water, and still more the 

 deep ravines of rivers and water-courses, abounded with the 

 malarious poison. At Basseterre, Guadaloupe, a guard-house 

 placed at the conflux of the inner and outer ditch of the fort, 

 infallibly affected every white man with fever that took a 

 single night-guard in it ; and the houses that were built in the 

 ravine of the river aux herbes, (a clear rapid mountain-stream 

 that runs through the town) or opposite to its " bouchure," 

 proved nearly as unhealthy as the guard-house above men- 

 tioned. 



Another proof, that from the attraction above mentioned it 

 creeps along the ground, so as to concentrate and collect on 

 the sides of the adjacent hills, instead of floating directly up- 

 wards in the atmosphere, is the remarkable fact, that it is cer- 

 tainly 



