Radiation in determining the Site of Malaria. 329 



effluvia, as we witness among the various combinations of the 

 chemical world ? Withdraw one of the elements of a binary 

 compound, and the other becomes immediately apparent, and 

 is developed with all those potent qualities which had been 

 destroyed or neutralized whilst in union. So miasmatous mat- 

 ters are inert while fixed to the ground, from which they can 

 arise only in conjunction with caloric ; and as long as they 

 continue together no ill effects ensue : but diminish the tem- 

 perature, or, in other words, take away the caloric, and the 

 injurious qualities of the miasms immediately become appa- 

 rent. It may be objected, that if the injurious agency of mi- 

 asmata in the air results from the mere abstraction of heat, no 

 reduction of temperature could ensue without the production 

 of malaria. — But this is not true ; for we may justly suppose 

 that in a great majority of cases there is not sufricient noxious 

 matter on the ground to saturate — if I may be allowed the 

 term — the caloric existing in the air, and therefore that in these 

 instances great reductions of temperature may take place with- 

 out any appearance of malaria, in the same manner as (to carry 

 on the analogy drawn from chemical combinations) we can 

 detach a portion of the acid from a supersaturated salt, with- 

 out developing the existence or qualities of the alkali. On the 

 other hand, the miasmatous source may sometimes afford a 

 supply amply sufricient to satisfy even a very high temperature; 

 and then any trifling escape of caloric will be accompanied 

 with an injurious precipitation : and if the cooling process con- 

 tinues, a highly noxious malaria will result. 



It has been observed, that very often the diseases arising 

 from malaria ensue upon the temperature of a place reaching 

 a certain point ; that they increase in frequency and violence as 

 the heat increases, but diminish as the mean temperature falls. 

 These facts are not at all irreconcileable with the phenomena 

 of radiation; for in these cases we may justly suppose, that at 

 the higher temperatures malarious matter is liberated from the 

 soil, the quantity of which is greater in proportion to the ther- 

 mometric rise, while the lower temperatures are not sufficient 

 to liberate any quantity of the noxious effluvium and diffuse it 

 through the air : in the former case the radiation of caloric 

 will be attended with disease, in the latter it will not. 



I might here relate many facts tending to show the inti- 

 mate connection w r hich subsists between caloric and miasma- 

 tous effluvia, but I conceive that what has been here stated 

 will be ample to establish this point, as well as the fact that the 

 latter become virulent in proportion to the abstraction of the 

 former by the process of radiation. 



In conclusion, I shall briefly point out the importance of 

 New Scries. Vol. 4% No. 23. Nov. 1828. 2 U the 



