CHAPTER III. 



OCCASIONAL INGREDIENTS IN THE AIR. 



AT the extreme end of the valley upon 

 which we are supposed to be looking lies a flat, 

 marshy district, over which in the dewy even- 

 ings we may often see suspended a dense cloud 

 of vapour. The whole area of this district is 

 not above three or four square miles, yet its 

 inhabitants are more frequently in ill health, 

 and the annual proportional mortality is greater 

 there than in any other portion of the plain 

 beneath us. Were we to question them, they 

 would inform us that when in the hot weather 

 of autumn a current of air blew across the 

 marsh, they might certainly expect attacks of 

 ague to ensue. Their very countenances betray 

 their ill-health, and the long and sallow faces of 

 some are so peculiar, that we may well exclaim, 

 What can be the cause of this unhealthiness ? 

 The inhabitants say it is the marsh air. When 

 the same sort of district and effects occur in 



