284
( 12 )
Surface floats constructed of wood were also set adrift and watched during the day, but their course followed so closely on that of the sunken vanes that further observation of them was abandoned soon after sunset as unnecessary. A boat with adequate crew was detailed to watch the drifting of each float and to follow it day and night, and having a steam-launch at our disposal we were able to visit each float periodically and to note its change of position,
On the plan submitted herewith the relative positions of the several floats at the various times of our visits are shewn, the approximate course between each observation being sketched in. I will now briefly describe the courses of the floats.
On the morning of February the 27th (during the North East Monsoon) at 10.15 A.M. float No. 1 was set adrift off North Point on the ebb tide, the course followed by this float is indicated in the plan by n red line.
At 10.80 A.M. float No. 2 was started about three quarters of a mile cast of North Point; its course is indicated by a blue line.
Both these floats got into an eddy in Quarry Bay, No. 2 grounded in shallow water and on being moved out to the position of the surface float it closely followed the course of No. 1.
At 11 A.M. float No. 3 was set adrift off North Point and nearly made the Lyemun Pass; its course being indicated by the green line.
At 12.80 P.M. No. 4 was started off North Point; its course is indicated by the brown line.
At 1 P.M. No. 5 was started about a mile and a half cast of North Point; its course is indicated by the yellow line.
The tide turning shortly after 1 P.M. a strong current set in through the Lyemun Pass carrying the floats westwards.
At 2.55 P.M. float No. 6 was started off North Point on the flood tide; its course is indicated by a red line.
This float passing to the west of Green Island found its way out to sea on the afternoon of the following day.
At 5.15 P.M. float No. 7 was started off North Point, after travelling a short distance westwards this float returned on the ebb as far as the Lyemun Pass but missing the mid channel current returned on the flood, Its course is indicated by a blue line.
At 6.45 PM. No. 8 was set adrift off North Point and after travelling westwards for four hours it returned on the ebb and passed through the Lyemun Pass at 2.30 Its course is indicated by a brown line. This completed the float experiments at North Point.
A.M.
On the following day, February the 28th, a similar series of experiments was effected at Belcher's Point. At 8.45 A.M, No. 1 was started on the ebb tide and taking a westerly course, as indicated by the red line, got into shallow water to the north-west of Green Island. On being set free again this float continued its westerly course round Green Island and turning southwards made for the open sea.
At 11 A.M. float No. 2 was started and passing direct through the Sulphur Channel gained the sea; its course is indicated by a blue line.
At 1.45 P.M. No. 3 was started and also passed through the Sulphur Channel, but meeting the flood tide was carried in a north westerly direction outside of Green Island; its course is indicated by a brown line.
At 3.50, 5.10 and 6 r. respectively, Nos. 4, 5 and 6 were set adrift. These as indicated by the blue, red and brown lines made little progress.
At 9.25 4.3. on the 21st of August during the South West Monsoon iloat, No. 1 started on the cbb tide, got into slack water off the west point of Quarry Bay, and remained almost stationary until the turn of the tide when it proceeded westwards arriving off the south of Stonecutters' Island at 10 P.M. During the following ebb it returned as far as Kowloon Point, and during the next flood it was carried back to the south of Stonecutters' Island arriving to the south of its previous position at 8 P.M. shewing a tendency to leave the harbour westwards; its course is indi- ented by a red line.
( 13 )
At 10.5 P.M. No. 2 was started and went direct through the Lyemun Pass arriving at the Pass in one hour; its course is indicated by a blue line.
At 1.20 p.m. No. 3 was started; making but little progress eastward it was carried on the flood through the harbour as far as the Canton Wharf returning thence as far as Causeway Bay on the following ebb tide; its course is indicated by a green line.
At 3 P.M. No. 4 was started on the commencement of the flood, and after passing North Point ou the flood tide followed practically the same course as No. 1.
At 4.45 and 6.15 P.M. Nos. 5 and 6 were started and left afloat till the night of the 22nd. No. 5 would probably, on the following ebb tide, pass North Point, aud No. 6 would follow somewhat the same course as followed by Nos. 1 and 4. course of each of these floats is indicated by green and blue respectively.
The
At 8.15 A.M. August the 22nd No. I was started off Belcher's Point and took an easterly course past North Point; on the following flood it drifted back a little to the west of that Point and would probably have got into the mid-chaunel cur- rent on the following ebb and been carried through the Lyemun Pass; its course is indicated by a brown line.
At 10.15 a.m. No. 2 was started and after progressing down the Sulphur Channel for soure distance returned on the half ebb, arriving off the Canton Wharf at 10 P.M.; at the end of the flood it would take a north-westerly course and would probably be carried thence up towards the Canton River on the next flood, passing out west of Green Island on the following ebb; its course is indicated by a red line.
At 12 o'clock No. 3 was started. Taking an casterly course it reached Yau- mati bay at 6.10 P.M., and after sweeping round on the flood in a south-westerly direction it took an easterly course arriving off the Cantou Wharf at 10.35 r.M., at which hour the commencement of the next ebb would probably take it eastwards past North Point; its course is indicated by a green line. At 2.25 P.M. No. 4 was started and travelled eastwards slowly; its course is indicated by a blue line. 5.40 P.M. No. 5 was started on the flood tide but made little progress; its course is indicated by a red line.
AL
With respect therefore to a sewage out-fall at North Point it appears from these experiments:-
(1.) that during both the North East and South West Monsoons there is a strong tidal current tending to carry all matters held in suspension in the waters of the harbour at or about North Point through the Lyemun Pass during the ebb tide, and that this tendency extends as far as Kowloon Point during the North East Monsoon. (i.) that during the North East Mousoon the flood tide sweeps through the harbour and effects a general dispersion of all suspended matter, and that there is also a strong current round Kowloon Point towards the South of Stonecutters' Island.
(ii) that during the South West Monsoon the general tendency of the flood tide is to carry suspended matter from North Point through the harbour towards the mouth of the Canton River.
And with respect to a sewage ont-fall at Belcher's Point it appears from the experiments
---
(1.) that during the North East Monsoon the ebb tide will probably carry
all suspended matters out to sea to the south of Green Island. (ii) that the flood tide has little effect at this Point either during the
North East or South West Monsoon.
(ill.) that during the South West Monsoon the ebb tide sets in an easterly
and north easterly direction.
From the foregoing I am of opinion, considering the depth of water and strong tidal currents that exist in the harbour during the whole of the year leading to the general dispersion and mixing of all foreign matters with the tidal waters, that no nuisance will arise from the placing of sewer out-falls at Belcher's and North Points, and it is on this account that these two Points have been selected as suit- able out-fall stations.
No comments yet.
Private notes are available after approval.