556 REPORT—1896. 
The system, however, gave such evidence of ultimate success (provided 
the material was of a suitable character) that further experiments were 
successfully made at that time on the sandbanks within the river. When, 
therefore, there appeared a possibility of success warranting an experi- 
ment in dredging the Mersey Bar, the experience in pump-dredging indi- 
cated the method to be adopted, and the adaptation and use of two of the 
Board’s 500-ton steam hopper barges, followed in course by the construc- 
tion and setting to work of the gigantic dredger Brancker, novel in many 
features besides her size, of 3,000 tons capacity, and capable of filling 
herself in about three-quarters of an hour, resulted in a notable ameliora- 
tion of the condition of the Bar. 
From a channel, having in 1890 a minimum depth of 11 feet at low 
water of lowest tides between the fairway buoys, the Bar has now cut 
through it a channel 1,500 feet wide between its buoyed alignments, with 
a minimum depth of 24 feet—and so small a depth only in a few isolated 
patches over its area—by far the greater portion ranging to a depth of 
28 feet. 
It is fortunate that so important an improvement of the access to the 
port has been secured at a time when the enormous growth in the size of 
ships, the frequency of their voyages,.and the urgency of trade competi- 
tion absolutely demanded some advance of the kind. This achievement 
has not, of course, been attained without considerable expenditure, of 
which the cost of the two 3,000-ton dredgers (the Brancker above referred 
to having been followed by the G. B. Crow, of like capacity), which had ta 
be specially designed and constructed for the purpose, forms an important 
item. The total quantity of sand removed to this date (September 1896) 
and deposited in a safe position, whence it cannot return to its old site, 
amounts to 15,511,390 tons, the actual cost of the operation being at the 
rate of 1}d. per ton. A description of this work has been so fully and 
exhaustively given in the paper read to the British Association last year 
by the author’s son and chief assistant, Mr. A. G. Lyster, that it is un- 
necessary here to enlarge further on the subject beyond stating that since 
last year costly additions have been made to the plant, which, by mini- 
mising the chance of a breakdown, still better ensure a successfu} 
issue. 
The subject of the tides may be considered as collateral to that of the 
channels. They are another important feature in the welfare of the Port, 
demanding some slight notice, and as a preliminary it may be well to 
explain the standard by which local tides are measured. 
The datum level, long since arbitrarily adopted for all engineering 
work in connection with the Mersey, is that of the level of the sill of the 
first dock constructed, which has long since disappeared, but the level has 
been transferred to the bench mark on the wall of one of the more 
recently constructed pier-heads. This local datum is known as the ‘Old 
Dock Sill.’ 
Several years ago a Committee of the British Association considered 
closely its relation to other standard levels, and its relation to Ordnance 
datum was then determined to be that the latter was 4°67 feet above Old 
Dock Sill. It may be noted in passing that the Ordnance datum was 
settled from observation taken by Royal Engineers of the mean level of 
the sea at Liverpool during a certain month in the year 1841. The rela- 
tions of a number of important tidal levels to Old Dock Sill, mostly taken 
