328 PHILOSOPHICAL TRANSACTIONS. [aNNO 1778. 



examples of the noxious effects of the effluvia from putrid bogs and marshes. 

 Thus the experiments prove, that marsh effluvia are poisonous to a living animal; 

 yet they may probably act as an antiseptic on the dead one. Fixed air is a 

 powerful antiseptic in the one, but is deadly to the other. Nitrous air preserves 

 all flesh from corruption after death ; yet let any living animal but once breathe 

 in it, and it instantly expires. Some of our bogs have the singular property of 

 preserving dead bodies not only sweet but pliable for many years ; but we are 

 certain they are at the same time deadly to living animals. 



Exp. 11. A 4th part of an 8 oz. phial was filled with the same mud as in the 

 last experiment, but so much dried in the sun as to be easily rubbed into a 

 powder, the rest being air ; after being corked, they were set by for 24 hours, 

 and in the interim frequently agitated. The air being at the end put to the test 

 was scarcely altered, the greatest diminution in several different experiments was 

 only from 6'1° to 6o°. So that the air was yet quite good, though they stood 

 double the time of that in the last experiment. Hence it is evident, that bogs 

 and marshy grounds, when dry, or perfectly drained of their moisture, become 

 healthy, and emit no noxious exhalations. This illustrates the observation, that 

 such situations are not liable to produce their peculiar diseases during the dry 

 seasons, or after being well drained. And it is observed, that in the most un- 

 healthy of our settlements in Africa, the East and West Indies, the inhabitants 

 are at such times healthy. But when the wet seasons begin, the scene is re- 

 versed ; the air immediately becomes vitiated, polluted, and destructive ; putrid 

 fevers arise, and spread destruction over the country. The ingenious Mr. Ives 

 gives a dreadful instance of this, and of the diabolical revenge of the Arabs, 

 when they think themselves injured by tlie Turks at Bassora : by breaking down 

 the banks of the river near that city, they lay all its environs under water. 

 After the water is nearly evaporated, the mud and other impurities corrupting, 

 pollute the air to such a degree, as to cause a most mortal fever in that populous 

 city. This was the case when Mr. Ives was there: of this fever 14,000 souls 

 perished ; and of the Europeans settled there only 3 escaped with life : a most 

 horrid mode of revenge, and a dreadful example of the deadly eflects of marshes 

 and stagnant waters in hot climates. Let us see if we can prove this by actual 

 experiments. 



Exp. 23. To the same powdered mud used in the last experiment, was added 

 as much water as was required to bring it to the same consistency with that in 

 the 2lst experiment. Tiiis being inclosed with 6 oz. of air as before, stood 24 

 hours. The air had then contracted a noisome smell, like a new-cleaned ditch, 

 and was diminished from Ql° to 49". Several experiments gave the same results : 

 on standing longer, it was diminished from 62" to 29°. This experiment proves 

 and illustrates the effects of moisture co-operating with unhealtliy soils in pro- 



