BILIOUS anp INTERMITTING FEVERS. 209 
prevent the difeafes that have juftly been afcribed to them. 
Let the trees be planted in the greateft number, and clofeft 
together, to leeward of the ordinary current of the fum- 
mer and autumnal winds. I have known feveral inftances 
of families being preferved from fevers by an accidental 
copfe of wood ftanding between a mill-pond and a dwell- 
ing houfe, and that in cafes too where the houfe derived 
no advantage from an high fituation. The trees around 
or near a mill-pond, act perhaps in a {mall degree mecha- 
nically. . By fheltering the pond from the action of the . 
fun, they leflen exhalation, as well as obftruct the paflage 
of the vapors that are raifed to the adjacent parts. But 
they act likewile chemically. It has been demonftrated 
that trees abforb unhealthy air, and difcharge it in a high- 
ly purified ftate in the form of what is now called ‘ de- 
“ flogifticated” air. The willow tree, according to Mr. 
Ingenhaufz, has been found to- purify air the moft rapidly 
of any tree that he fubjeCted to his experiments. The ra- 
pidity of its growth, its early verdure, and the late fall of 
its leaf, all feem to mark it likewife as a tree highly pro- 
per for this purpofe.. 
A fecond method of preventing fevers, is to let the cul- 
tivation always keep pace with the clearing of our lands. 
Nature has in this inftance conneted our duty, intereft 
and health together. Let every fpot covered with moifture 
from which the wood has been cut, be carefully drained, 
and afterwards ploughed and fowed with grafs feed; let 
weeds of all kinds be deftroyed, and let the waters be fo 
directed as to prevent their ftagnating in any part of their 
courfe. 
Thefe are the two principal means of extirpating inter- 
mitting and bilious fevers from our country, but as thefe 
means. are flow in their operation, I fhall fubjoin a few 
direCtions for preventing fevers till the above remedies 
can take effect.. 
r. Whether 
