Mr. m Ann’s 'freatife 
55 8 
SECTION I. 
Different ufes for which canals are made , with an account 
of the principal authors who have wrote concerning 
them. 
i. Artificial canals are to be confidered in a double 
light ; as facilitating commerce by means of internal navi- 
gation, and as preventing inundations by carrying off the 
too great abundance of water from low and fiat coun- 
tries, fuch as are Holland, Flanders, &c. In thefe laft 
named countries they ferve at once for both purpofes ; 
and it is in this double light that I fhall confider them in 
the enfuing difcourfe. If canals for draining have fluices 
upon them, particularly at the end whereby they dif- 
charge their waters, as is univerfally the cafe in the Low 
Countries, they differ in no wife from navigable canals : 
if they have nothing to fuftain their waters in them, they 
are to be confidered in every refpedt as rivers or rivulets, 
and follow the fame laws. It muft, therefore, be care- 
fully kept in mind, that whenever I mention canals, I 
mean thofe only whofe waters are kept up by fluices, 
aiuf never thofe without them, which I include, without 
diftindtion, under the common appellation of rivers ; for 
they 
