On Malaria. 323 
efficacy ; and for this purpose I beg leave to quote the instance of 
reclaiming the Val de Chiana, to shew that physical causes may be con- 
trolled, by the skillful application of human industry. 
Near the city of Crotona-was a lake, of no very great dimensions, 
but surrounded with marshes which diffused the most pestilential ex- 
halations. ‘The Tuscan genius and spirit, at that time in its zenith, 
suggested and executed a plan for draining the lake and its marshes. 
A canal leading to the Arno carried off the water, and three thousand 
acres were brought into cultivation. It was not thrown into a vast 
domain, and consigned to some individual proprietor, in whose hands 
the neglected parts would soon have run down the remainder, but 
was divided into seventy farms, which were separated by roads, and 
bordered with canals. On each farma rural dwelling was erected 5 
every inch of ground was cultivated; the crops, consisting of corn, 
wine, vegetables and silks were gathered in season, and not a foot of 
land was left to run waste. ‘The plain of Crotona in 1813 dis- 
played one of the noblest triumphs of human industry ;”* fertile 
fields where had been a pestilential morass, a salubrious atmosphere, 
and an industrious and happy population. Volney states that he “ wit- 
nessed the drying up of a small pool and rivulet in Holland completely, 
to free a family from the annual visits of intermittent fevers.” I might 
illustrate this part of the subject with many examples from foreign 
countries, in proof of the salutary effects of draining ; particularly the 
benefit produced to the health of the inhabitants, by reclaiming 
large tracts of fens and bogs in the eastern counties of England, a 
benefit felt even in the metropolis; and a few cases nearly analogou 
in the United States might be cited ; but I am not aware that the ex- 
periment has been thoroughly tested in this country. : 
In order to make the draining effectual, ditches should be broad and 
deep enough to convey off the superfluous water of the rains; and 
cross cuts or sluices should lead from hollows to the main outlet. No 
weeds should be allowed to grow on the banks, and the bottoms should 
be scraped annually, to clear them from mud and aquatic plants. 
lt is ‘of particular service to cut the weeds, grasses and shrubs, after 
the coming of frost, and to burn them upon the marsh ; as the ma- 
terials, which would be injurious in the following hot season, are thus 
changed into a species of manure, that hastens the progress of the 
* Chateauvieux’s Travels. 
