280 JOURNAL OF THE PLYMOUTH INSTITUTION. 
the Eddystone rocks, or the proximity of a strong stream, and to 
what extent all these influences contribute to its formation—I am 
unable to say; but early in the flood there is extending from the 
Lighthouse towards the west of the Sound a tide-lining, showing 
that a coalition of some sort takes place. The currents about the 
Lighthouse, as its name indicates, are exceedingly complicated, and 
very far from being understood, although they have been known so 
long; and on the present occasion have not the same interest to us 
as those inside the Breakwater. 
The flood tide, then, first sets into Plymouth from a south-east 
or easterly direction, and may be observed from Penlee Point 
making fair into Cawsand Bay, round which it sweeps gently, and 
is soon seen creeping up towards the Bridge, under and past 
Picklecombe Fort; but as yet the currents are very feeble. A 
considerable body of water passes into the Sound at the eastern 
channel, and setting rather against the rocks, just after the estab- 
lishment of the western stream. At about one and a-half or two 
hours after low-water on springs the flood has acquired considerable 
velocity, and runs fair into the Sound from the south, or nearly so. 
The Breakwater necessarily very much intercepts its progression 
into the bay, and, as would be the case with any similar obstacle 
in a stream, the currents opposite its ends are accelerated from one 
knot outside to something like two or three, while on the seaward 
face there is an area of confused and involved currents, caused by 
the sudden stoppage of a strong stream. At either end, on the 
seaward face, small counter currents are sometimes observed lying 
inside the line of the Breakwater, evidently eddies caused by the 
strong stream passing the end of the Breakwater. On the inside 
of the Breakwater, and at its western end, a very much more 
important eddy takes place, so much so that we might almost 
call it a feature in the navigation of the Sound at half-flood 
tide. 
A much larger body of water comes into the Sound through the 
western channel, and generally at a higher velocity, than through 
the eastern, which latter current loses much of its strength from 
impinging on the adjacent rocky coast. The western side of this 
same stream through the eastern channel spreads out immediately on 
passing the end of the Breakwater, where it breaks up into uncer- 
tain streams along its eastern half. Curiously enough, no important 
eddy is formed by this eastern stream, at all comparable to the one 
