[ SI ] 
II. On the Tides. By John William Lubbock, Esq., V.P. and Treas. R.S. 
Read November 17, 1831. 
When I was lately at Paris, M. Bouvard kindly allowed me to copy some 
of the Observations made at Brest. Since my return to this country, the obser- 
vations I obtained have been discussed by M. Dessiou, with regard to the 
principal inequality, or that which is independent of the parallaxes and decli- 
nations of the luminaries and depends solely on the moon’s age, that is, on the 
time of her passage through the plane of the meridian. 
The result is exhibited in the following Table. 
Table showing the interval between the Moon’s Transit and the time of High 
Water at Brest, from the Observations made there in the year 1816. 
Time of 
Moon’s 
Transit. 
Interval 
Observed. 
Moon’s 
Transit. 
Interval 
Observed. 
Moon’s 
Transit. 
Interval 
Observed. 
Moon’s 
Transit. 
Interval 
Observed. 
h m 
h m 
h 
m 
h m 
h m 
h m 
h 
m 
h 
m 
0 0 
3 47-8 
3 
0 
3 7-8 
6 0 
2 52-8 
9 
0 
4 
9 
0 30 
3 43*5 
3 
30 
3 4-9 
6 30 
3 2-2 
9 
30 
4 
9-9 
1 0 
3 36-6 
4 
0 
2 58-4 
7 0 
3 18-2 
10 
0 
4 
9-5 
1 30 
3 23 
4 
30 
2 50 
7 30 
3 33-5 
10 
30 
4 
6-9 
2 0 
3 15-5 
5 
0 
2 48-5 
8 0 
3 46-4 
11 
0 
4 
2-5 
2 30 
3 10-9 
5 
30 
2 49-5 
8 30 
4 0 
11 
30 
3 
54-6 
It appears from this Table, that the establishment of that part of the port 
of Brest where these observations were made is 3 b 48 m ; the Annuaire for 1831 
gives 3 b 33 m for that quantity. The constant X — \ may be taken about 
l b 20 m , or 20° in space, being the value assigned to it by Bernoulli, but differ- 
ing considerably from its value in the port of London, which is 2 h , or 30° in 
space. This result is important, as showing, unfortunately, that Tables of the 
Tides for London are not applicable to Brest by merely changing the establish- 
ment, that is, by adding a constant quantity, as has been supposed hitherto. 
The same remark applies of course generally to any distant ports. 
The preceding Table giyes also = tan 18° 45' about, the logarithm of 
h 2 
