864 On Drainage and Sewerage of Towns. 
this I would obserye, that the evidence given to the Health 
of Towns’ Commissioners was sufficient to prove that in the 
towns of England the application of a proper system of 
cleansing and draining reduced the mortality in those dis- 
tricts in which fever constantly prevailed to an extent of one- 
third, or even, in some instances, of one-half; and although 
such a system would not remove the eyils arising from over- 
crowding the habitations of the poor, or from the faulty 
construction of the buildings in which they reside, yet, by 
creating a better atmosphere around them, many of the 
most active causes of disease would be neutralized. 
Twill proceed, therefore, to enquire into the principles by 
which a proper system of drainage should be regulated, 
and then discuss the best mode of applying these principles 
to the drainage of Hobart Town and Launceston ; and I will 
lay before the Society such information as to the construction 
of sewers, their size, form, and the materials of which they 
may be composed, as may afford useful hints to those upon 
whom has devolved by law the charge of superintending the 
drainage and cleansing of these towns, besides enabling them 
to form an approximate estimate of the cost of such an 
undertaking. 
We are met at the outset of an enquiry of this kind, by the 
fact that the character of the drainage must be to a great 
extent dependent upon the nature of the supply of water 
furnished to the inhabitants; and upon consideration this 
will appear perfectly clear. With a large supply of water, 
much must pass through the sewers; and again, these will 
be more easily cleansed and kept in order where the rush of 
water down them is frequent and large. 
As a preliminary, therefore, to any enquiry into the drain- 
age of towns, it is necessary to say a few words as to the 
supply of water, which is not only essential to good drainage, 
