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VII. Tide Observations at Otaheite, or Tahiti. 
By Captain Sir E. Belcher, R.N. Communicated by Captain Beaufort, R.N., 
F.R.S., 8fc. 
Received October 31, 1842, — Read February 16, 1843. 
H. M. Ship Sulphur, Spithead, 
0 July 22, 1842. 
SIR, 
WlTH reference to that part of my instructions relating to noon high water at the 
Island of Otaheite, or Tahiti, I now transmit to you fair copies of the tide-journal 
registered at the island of Motouta, in the harbour of Papiete, as well as a short 
comparative series made at Point Venus. 
The island of Motouta, the position before named, is the property of the Queen, 
and therefore free from intrusion or likelihood of disturbance. It is situated well 
within the reefs, upon a coral flat, and any wave tumbling over the reef would expend 
itself before reaching the island. 
It is, at the same time, within the direct influence of the deep water channel, to 
seaward, but entirely protected by the reef. The swell does not enter by reason of 
the overlapping tongue of the northern reef, which, projecting westerly, receives and 
throws off 1 the sea obliquely. The gauge was placed in ten feet of water, and the 
batten in four. 
In order to prevent any confusion, by change of observers, and thus destroying the 
interest which a single individual would feel if entrusted with the sole execution of 
this interesting duty, I selected one of my old followers, Mr. M c Kinley Richardson, 
Mate, and placing him in entire charge of the island, furnished him with a tide- 
gauge of my own construction, as well as a tide-batten. 
The tide-gauge was constructed as follows (Plate IV.) : — A square wooden trunk 
of six inches aperture, a a, was closed at the bottom, but admitted water by small 
lateral holes, b b, six inches from the bottom. This was to prevent any sudden wave 
which might roll in from affecting the mean level. 
Within this trunk floated a glass cylindrical jar c, five inches in diameter by eleven 
in height, and ballasted with sufficient small shot to half immerse it. It was rendered 
air-tight by means of the gauge-rod which screwed into an interior stuffed pad against 
the collar of the exterior. 
The end of this rod was of brass, where it screwed into the float, but for ten feet 
above was of very light, tough cypress, half an inch in diameter. 
At the summit of the trunk a cap was fitted, d , having three friction rollers, through 
