68 
JYutes on the 
result of 115 observations taken three miles within the 
entrance gave 11 •> 48 m for the time of high water on the 
full and change day, orO h 18 m before the moon passes the 
meridian. The rise of tide was irregular, the least being 
4 and the greatest 10 feet. The greatest rise noticed was 
during the neaps, when a N.W. gale forced the water back. 
The tides flow 5' 1 50"’, and ebb 6 h 25m, with a velocity 
varying from 2 to 5 miles an hour, according to the con¬ 
fined or open space of the river the stream traverses. 
The light-house at Low Head (41° 3' 26 v S., 146° 50' 
16" E.) is elevated 140 feet above the level of the sea, re¬ 
volving once in 50". 
I subjoin a few notes already published on the dangers 
in the Tamar, with the marks for avoiding them. - 
The most formidable shoal in the entrance of Port 
Dalrymple bears the name of the Middle Ground, a rooky 
patch, reported in one spot to have only nine feet at low 
water spring tides. But the least water found on it by 
the Beagle’s boats w r as twelve feet. The first black cliffy 
projection eastward of Low Head, in one with the ex¬ 
treme point of the latter, or the flag-staff on Low Head, 
open northward of the light-house, clears the northern 
edge of it. 
The leading marks for entering eastward of the Middle 
Ground, generally called the Eastern Channel, are the 
Shear Beacon and Dr. Browne’s house, the first one mile 
inside the western entrance point. The Shear Beacon 
must be kept a little open to the left or southward of the 
house, until getting abreast of the light-house, when the 
beacon should be kept in one with the centre of the house. 
When within cables of the Shear Beacon, the course 
should be changed to the direction of the Barrell Rock 
beacon (the first on the eastern side), to avoid a patch 
of kelp extending 1 J cables in an easterly direction from 
the Shear Beacon; the depth there is nine fathoms, and 
