On Malaria* 301 



contain the elements of a marsh, or are distmguished by a 

 vegetation accompanied by water. Whatever these may be, 

 let their names be what they may, or their appearances as 

 deceptive, they are at least suspicious, and in very many cases 

 they will be found to be real causes of the diseases of malaria, 

 wherever the temperature, or the season and climate, are 

 favourable, while that these are so with us I have just shown. 



In a general enumeration, I may name the following places 

 or soils, before proceeding to such particulars as may be neces- 

 sary in explanation. Besides proper marshes, fresh and salt, 

 meadows, or wet pasture-lands generally, however situated, 

 there are woods, coppices, and thickets, plashy and limited 

 spots of grounds, sea walls and river embankments ; and, as 

 falling better under the head of water, lakes, rivers, and ponds, 

 including mill-dams, ornamental waters, canals, and the pools 

 of insignificant dimensions which occupy commons, gravel-pits, 

 or other similar places, together with agricultural ditches and 

 drains of all kinds. To these, I must also add, as coming under 

 the heads of vegetable matter without vegetation, sewers and 

 town-drains, dunghills, tide-harbours, flax-ponds, or other re- 

 ceptacles of putrefying vegetables, and lastly, at sea, bilge water. 



With respect to the most common of causes, though it is often 

 thought, in England, that salt marshes are not insalubrious, 

 and, very particularly, that security is obtained whenever they 

 are daily washed by the tide : an ample experience shows that 

 they are as pernicious as fresh-water ones, and that a daily tide 

 is no security. Some of the most poisonous tracts in Europe, 

 indeed, in France, Spain, Italy, and Greece, are salt marshes; 

 and of how little value or protection the sea is, is fully proved 

 by the tide-rivers of the tropical climates, most notoriously the 

 most pestilential places that exist, even in those destructive 

 regions. Where such tracts are found in England I need not 

 say, as they are always both obvious and well known. 



It is not believed with us, that meadows can produce malaria : 

 this is to be questioned, in the first place, on general principles, 

 and from other European experience ; and secondly, it can be 

 proved by domestic experience, that they actually are the 

 causes of fevers with us ; and even independently of their ditches 

 or drains, which, it must be observed, may often produce 



