of Edinburgh, Ses^fM' 18 84-85. 
89 
grass level in the Mersey, where we find combined every one of 
these characteristics of danger, which is not the case in any of the 
other rivers referred to. Not only so, hut in every case those 
characteristics are more strongly marked. To all this must be 
added the all-important fact that if silting take place, as mus-t 
be expected, there seems no practical mode of remedying the evil ; 
for, owing to local circumstances, the walls cannot be extended 
so as to shelter the bar, as that would require no fewer than 
ten miles of breakwater to be erected in the stormy waters of 
Liverpool Bay. 
But while the erection of training walls on the Nith, Lune, and 
Kibble has thus been followed by large deposits of silt, it is still, 
and with truth, contended that these navigations have been, upon 
the whole, greatly improved. 
We are here thrown back once more upon the question of ratio 
between the effects for good and evil; of ratio between the extra 
amount of tidal water gained by deepening and enlarging the mid- 
channel, and the amount of scouring water altogether excluded by 
accretion in the land-locked estuary, on which ratio, as already 
stated, the whole question mainly depends. 
But how is the value of this ratio to be determined, and what 
limit is it safe to observe ? 
I can only here refer to the case of another river, not yet alluded 
to, viz., the Tay, which, during the years 1833 to 1844, was im- 
proved according to designs of my late father, so that an additional 
depth of 4 feet and a tidal acceleration of 50 minutes were got up 
to the quays at Perth. But no training walls were ever proposed to 
be erected in the lower and wider part of the estuary, where there 
is sand and silt. 
In the year 1845, however, certain riparian proprietors proposed 
to embank land in the lower and wider estuary, and the authorities 
of the important harbour and docks of Dundee became alarmed for 
the safety of their interests, and applied to the Admiralty to send 
an engineer of eminence to report on the whole subject. The 
engineer selected was the late Mr James Walker, the then per- 
manent President of the Institution of Civil Engineers, and the 
acknowledged head of the profession in all maritime matters. In 
an elaborate report he condemned the proposed works, on the ground 
