STUDY VII. 35. 



reaches, and in which the rain-waters ftagnate, 

 becaufe they are confined by the dikes and ditches 

 of the old falt-pits, are become confiant fources of 

 diftemper among the cattle. Similar difeafes, pu- 

 trid and bilious fevers, and the land-fcurvy, annu- 

 ally iflTue from the canals of Holland, which pu- 

 trify, in Summer, to fuch a degree, that I have 

 feen, in Amfterdam, the canals covered with dead 

 iifhes ; and it was impofTible to crofs certain 

 ilreets, without obftrufting the pafTages of the 

 mouth and nofe with your handkerchief. They 

 have, indeed, forced a kind of current to the flag- 

 nant waters by means of wind-mills, which pump 

 them up, and throw them over the dikes, in places 

 where the canals are lower than the level of the 

 Sea ; but thefe machines are flill far too few in 

 number. 



The bad air of Rome, in Summer, proceeds 

 from it's ancient aqueduds, the waters of which 

 are difFufed among the ruins, or which have inun- 

 dated the plains, the levels whereof have been in- 

 terrupted by the magnificent labours of the an- 

 cient Romans. The purple fever, the dyfentery, 

 the fmall-pox, fo common all over our plains, af- 

 ter the heats of Summer, or in warm and humid 

 fprings, proceed, for the mofl part, from the pud- 

 dles of the peafantry, in which leaves and the re- 

 fufe of plants putrify. Many of our city-diftem- 



p 4 pers 



