On Drainage and Sewerage of Towns. 865 
but operates beneficially upon the habits of the people, by 
encouraging and facilitating cleanliness. 
In both Hobart Town and Launceston thig supply is 
deficient. In Hobart Town, the source, though it may be 
said to be perennial, is trifling in amount; while in Laun- 
ceston, proper means have not yet been adopted for turning 
to account the ample streams discharged by the South Esk, 
alarge portion of which river might be directed through the 
town if necessary. 
In Hobart Town, the supply for many years, indeed until 
recourse is had to the water of the Derwent, will always be 
rather scanty; but by constructing reservoirs in the valleys 
above the town, a great body of water might be retained at 
an elevation sufficient to carry it through all the streets. 
To return to the consideration of drainage: the elements 
of which a general system is composed are ;— 
1st. Main sewers, by which the accumulated drainage of 
the town is carried to its outlet, wherever that may be. 
2nd. Branch sewers, by which the drainage of a certain 
amount of the area of the town is carried into the main 
sewer. 
8rd. House-drains, or small channels by which the drain- 
age of isolated buildings are discharged into the branch 
sewers. 
With regard to the main sewer or sewers, it is evident that 
the dimensions of these must be sufficient to carry off not 
merely the drainage of the buildings composing the town, 
but also that ofthe whole area which discharges itself into 
the same channels. 
In point of fact, the main sewer of a town often occupies 
the place of an old watercourse, which formed the outlet of 
the drainage of a large district, comprising not only the 
