MEETINGS OF SOCIETIES. 187 
somewhat complicated combination. The general tendency ot the 
waves is to heap up the sand-bar across the entire distance between 
the heads, with the exception of a narrow channel under the 
North Head, and occasionally there is a second channel at the 
South Head, but this is not permanently navigable. In attempt- 
ing to improve this entrance, the first thing to be considered is at 
what point should the entrance channel be fixed, and in fixing this 
point it is necessary to study the effect of the tidal waters from the 
North Créek upon the tidal waters of the river, and, if possible, to 
combine them into one concentrated stream, to act jointly upon 
one fixed point on the bar. Looking at the case with the above 
considerations betore us, it appears that the best point on which 
to focus our large available scouring power, would be in the neigh- 
bourhood of A on the plan, as near as possible in a direct line 
with the centre of the last reach of the river, and somewhat to the 
north line of the North Creek. Having determined this point, we 
have to consider what works would be necessary in order that the 
tidal and upland water scour might be concentrated at that point. 
Firstly: By the construction of a breakwater starting from the 
South Head, extending seaward for about 2000 feet in an easterly 
direction, the entrance would then be protected from the south 
and south-easterly weather; at the same time the tidal waters 
would be directed so as to improve the South Channel. Secondly: 
By the construction ot a wall from the pilot station in a south- 
easterly direction, crossing the sand-bank, and terminating by a 
breakwater of about the same length as the proposed south break- 
water, leaving an entrance of about 1500 feet between the extre- 
mities of the works. The northern works would protect the en- 
trance from the north-easterly and easterly weather, which, as is 
well-known, are the principal agents in heaping up bars; they 
would, in conjunction with the southern breakwater, direct and 
concentrate the tidal action on the bar, thus enabling the ebb-tide 
and upland water to carry the sand well out to sea. Considering 
the large amount of tidal water available, and the great depth of 
the sea a short distance from the entrance, there can be no doubt 
that in a short time after the completion ot these works, there 
would be a sufficient depth at the entrance to enable the largest 
steamer afloat to enter; moreover, the lower reach of the river 
being protected from the prejudicial action of the waves, and hav- 
ing its direction fixed by the position of the entrance, would soon 
make for itself a permanent deep channel. Judging from the effect 
of the works at Dublin, where an insignificant river has been made 
available for a first-class shipping trade, by the correct application 
ot sound principles, the author has every confidence in predicting 
that if works were carried out on the lines proposed this great 
natural highway, which is now closed to all except small steamers 
and coasting craft, would be available for our first-class inter- 
colonial steamers, the effect of which, as tar as enhancing the 
value of property and increasing the prosperity of this district, 
cannot well be gauged or, in these times of advancement, even 
imagined. After the maturest consideration of this case, the author 
feels convinced that by the application of the most modern and 
improved construction, these works could be carried out for a sum 
not exceeding £200,000 or £220,000. The Clarence is undoubtedly 
the most important of all the rivers of this colony running into the 
