282 JOURNAL OF THE PLYMOUTH INSTITUTION. 
westwards, and towards the latter half of the tide into Millbay 
from the direction of the Mallard. 
There is little doubt that the current during the first part of 
the tide is along the deep trough, and it is only when the tide 
has risen and is discharging a large and increasing body of water 
on the surface, in a direction nearly at right angles to the deep 
stream, that we notice the boilings and upheavings in places when 
we should hardly expect them in this locality. The deep trough is 
no doubt the main cause of the quiet and rapid change in direction 
of the large volume of water flowing in a westerly direction, under 
the Hoe, towards Millbay and Mount Edgcumbe, for even beyond 
the ladies’ bathing-place the stream sets westwards. As this stream 
flows past Millbay, a “‘ lining” or boiling-up may be seen from the 
end of Gill’s Pier and about forty fathoms distant. Such a dis- 
turbance as the above can only be caused by the under-current at 
times setting against the steep sides of the channel at this point, 
and thus creating an upward current which, in its approaching the 
surface, meets the top-current flowing in a different direction, and 
thus produces the well-known surface disturbance. Fortunately 
this disturbance only occurs when the currents are strong, for the 
effects of coming suddenly from a strong current into still water, or 
a reverse current, are found to be very inconvenient when taking 
ships into Millbay. 
From Millbay on the first of a flood the main stream suddenly 
sets towards the cottage on Mount Edgcumbe, or right into the 
bend of the trough, thus following its formation completely. The 
complications and disturbances arise from three causes. 1. Water 
projected over a strong under-current in an opposite or different 
direction. 2. The under-current dragging these top-currents into 
its own direction. 3. The results of the momentum of a large 
volume of water, some fifteen or sixteen fathoms deep, on leaving 
the main stream or impinging against rocks or other obstacles. 
We have now reached the area enclosed between the Bridge, the 
battery on Wilderness Point, Devil’s Point, and Eastern King, in 
following up the flood tide towards the Hamoaze. 
When the tide sets towards Ravenness Point, or into the bend 
of the trough, there is comparatively a small quantity of water 
flowing over the Bridge from the Channel. There is, however, a 
distinct current, and when this stream comes in contact with the 
main western current we have the well-known disturbance on the 
