Oe a — 
203 
to notice, unless to complain of their deterioration in order to 
obtain some concession, until his statements have come to be 
received with a considerable amount of reserve. 
The Severn, both in its fresh water and tidal parts, is too 
well known by the members of this Club for a detailed descrip- 
tion being necessary, except to observe that at the present 
time the Tewkesbury weir may be considered as the division 
between these two portions. While certain causes have largely 
altered the primitive condition of this river, and re-acted upon 
its piscine inhabitants, which alterations have been to a con- 
siderable extent occasioned, either directly or indirectly, by 
‘the requirements of an augmented population. Such influ- 
ences may be considered under the heads of obstructions, 
pollutions, and injurious modes of fishing. 
Obstructions, such as weirs, may extend across the entire 
width of a stream for the purposes of navigation, or else for 
the deflection of water for mills or the supply of towns, while 
such constructions must impede the upward passage of migra- 
tory fish, or even entirely prevent it, unless means, as fish 
ladders suitable for the purpose, are likewise present and kept 
in an efficient working order. When floods are excessive, so 
that the summit of the weir is entirely concealed, strong fish 
can surmount it, while others are incapable of stemming the 
current. Fish-passes, however efficient, cannot overcome all 
the deleterious influences of weirs, which invariably, more or 
less, arrest the progress of fish ascending to their spawning- 
beds. Shad, and perhaps twaite, may during flood time pass 
over weirs, but the flounder is unable to do so, unless there 
existed a gap in the structure extending downwards toward the 
bed of the stream, or else a lock fish-pass were constructed 
through its substance. While their action upon eels, lampreys 
and lamperns are questions which require more research than 
they have as yet received. These weirs, in a low state of the 
river, likewise entirely stop young or spent fish descending 
seawards, a subject but too little attended to. 
Weirs for working mills or supplying reservoirs act in 
either of the following ways; in the first, the water, after a 
P 
