274 Mr. Addison's Remarks on the Influence of Terrestrial 



who may possess opportunity and the means of entering into 

 this interesting branch of inquiry, towards the benefits their 

 labours are likely to confer upon us in a medical point of view*. 

 I have shown that all those situations where the radiation of 

 caloric goes on with rapidity, are occasionally, if not at all times, 

 extremely unhealthy; while others, where this process is dimi- 

 nished, are on the contrary much less obnoxious to disease. 

 I have shown that debilitated constitutions are invariably found 

 to regain the tone and vigour of health much more perfectly 

 and more quickly in places little influenced by radiation or 

 removed from the sphere of its effects, than in others exposed 

 to the depositions which it causes from the air; and I have 

 endeavoured to confirm these observations, by pointing out that 

 in the radiation of caloric may be found the cause of the acti- 

 vity of those exhalations with which the sun, in tropical cli- 

 mates especially, saturates the air : in fine, that in this impor- 

 tant process one of the principal causes of malaria will be 

 found. 



I shall here offer a few more facts in support of the views 

 I have taken. And as nothing has tended more to confirm me 

 in them than the perusal of Dr. Macculloch's Essay on the 

 Production and Propagation of Malaria, I shall proceed to 

 the consideration of some of the passages in that publication. 



" The careful observer will often perceive," says the Doctor, 

 "that there are certain determinate places without any marshes, 

 where fevers are almost annually prevalent; while other places 

 in the vicinity are almost wholly or nearly exempt. A proof 

 of this may be drawn from the fact that some localities are 

 known to be unhealthy as compared with other neighbouring 

 places. 



" Thus it is the vulgar remark, that in certain houses or 

 places a family is rarely without some sickness ; or, to use the 

 strong but coarse language in which it is generally stated, * that 

 the apothecary is never out of the house.' It is almost equally 

 familiar, that families which before had been healthy, have be- 

 come the reverse on changing houses or situations ; as in the 

 opposite cases, that they have recovered health by change of 

 residence. Of such facts as these there is no observer who 

 must not be able to recollect numerous examples." Again, 

 " If a gravelly soil is healthy, it is because its easy drainage 

 prevents the growth of that particular vegetation which is the 

 cause of malaria ; and if a clayey soil is the reverse, it is be- 

 cause by lodging superficial water it generates, however par- 



* Vide the last section of" A Dissertation on the Nature and Properties 

 o( the Malvern Water," &c. &c. 



tially, 



