On Malaria^, 48 



belief, and truth, respecting the poisonous effects of dew in the 

 hot climates; the supposed pernicious quality of this depending 

 evidently on the malaria by which its formation is accompa- 

 nied. And in this case it is probable that the evil arises, not 

 from a fresh or peculiar generation of malaria, but from the 

 mere fact that the moist atmosphere is a better conductor than 

 a dry one. 



Not to be unnecessarily minute, we thus also explain the 

 danger of exposure to the morning air in similar situations ; 

 the facts, as they relate to the conducting of malaria, being the 

 same, though the meteorological circumstances are somewhat 

 different. Hence, also, we see why the grey mists which hang 

 over wet grounds in the evening in our own climate, are 

 esteemed pernicious ; the truth, however, being, that they are 

 perfectly innocent at certain seasons and in certain places — as 

 in the greater part of Scotland, for example, or in those places 

 and at those periods where malaria is not produced. The dis- 

 tinction is valuable, because of the inconvenience of restric- 

 tions on this subject, and because to know where the hazard 

 really lies is to reduce those, and also to prevent the infraction 

 of rules by not extending them beyond what is necessary ; and 

 thus also by seeing what are the real dangers of what is called 

 night air, we more easily avoid them. Night air is avoided 

 now, under a false philosophy, because it is cold or damp, or 

 for some other vague reason; while the dangers from mere 

 dampness or cold are as nothing compared to those here pointed 

 out; which also occur precisely where they are least feared, 

 namely, in warm summer evenings, after refreshing showers, 

 and so forth. Hence it is that fevers are produced in summer, 

 in rural situations, and especially perhaps amid the most 

 engaging scenery, by evening walks and exposure to what is 

 naturally considered, as it is felt to be, a balmy and refreshing 

 sequel to a hot day. Let this be enjoyed where it can with 

 safety, and as it often may ; but such evening walks will not be 

 safe in any of those situations which I need not repeat here, 

 after having detailed them as I have done in the former paper. 

 And lest I should be accused of wishing to excite unnecessary 

 alarm, I consider, on the contrary, that it ought to be dimi- 

 nighed by these remarks ; because, if we taJie the whole of 



