18 
Trunk Drainage. 
drains which trickle toward its supply, must be viewed as a 
system of drains organized and complete in itself; and if imme- 
diate necessity forbid our beginning at once at the outfall or 
main channel, we must at least improve our smaller brooks with 
a reference to the whole train of which they are but a part. 
Having thus endeavoured to portray some of the larger and 
also the minor evils inherited through past neglect of rivers and 
brooks, it is now my duty to point out the difficulties to be 
overcome, and the means by which to accomplish the desired 
remedy. 
5. Existing Difficulties in the Application of a Remedy ivhich 
arise from the Claims of Mills, Navigations, Sfc. 
6. Best and Cheapest Modes of Dealing icith the aforesaid 
Clairns. 
7. Best Mode of Correcting Existing Evils, loith due regard ta 
Preserving the Requisite Moisture of Subsoil in existing 
Meadows and to Irrigation. 
I prefer leashing together these points of the discussion, and 
treating the whole question in connection with them. The ob- 
stacles to a better Tj;unk Drainage are physical and moral, — the 
former including the obstructions of mills, navigations, bridges, 
meadows, cScc, and the engineering difficulties of performing new 
works with less of damage than gain ; the latter embracing tlie 
claims of owners and holders, prescriptive and vested rights, pri- 
vileges of immemorial or acquired possession, considerations of 
equity, of common law, of custom, of economical and political 
expediency. So multifarious and complicated are these difficul- 
ties — comprehended in Nos. 5 and 7 — that it will be wiser to 
answer the inquiries involved in Nos. 6 and 7 by a reference to 
the means already put in practice in past and present times, 
rather than by advancing any tlieoretically deduced plans of our 
own. In pursuance of this method, and waiving for a time the 
consideration of the nature of the works themselves, let us look 
at the progress of legislation upon this subject, watching the 
various questions which from time to time arose, and seizing 
where we can a lesson for our guidance in the present emer- 
gency. 
It would be needless to speculate upon the probable motives 
which actuated our early progenitors to the first enterprises of 
general industrial utility ; how co-operation for mutual benefit, 
in drainage as in other matters, may have been begun by one 
generation, enforced as " custom" by the next, and so on, until 
perpetuated usage and precedent became authoritative as " law." 
But, eschewing technicalities, law cases, and decisions, we may 
just note the main principles of procedure which were gradually 
