REVIEWS. 
431 
souUi-east midway between Old Harry and Lobster Kocks. And it appears 
that lliis must liavc continued till nearly as late as 1700, and tiial it not liu:n, 
at least at no very remote date, that ehauuel iiadadcpth of above four fatlioiris. 
By tiiis date, liowevcr, the eastern dill's had been so far abraded as to briu;; tlie 
power of the channel waters to act energetically on the harbour ebbs, within 
the area of the present Hook, and by the middle of the last century the cluunicl 
had westcd more than a quarter of a mile, and its original bed became the one 
mile swash way, the swashway of Mackenzie, which long retained a depth nearly 
etpial to the present entrance; and tiie easternmost point of the Studland 
sands was then cut olf by tlic new channel, and became the point of the 
rapidly westing Hook. Ultimately the seventeenth century clianncl, after be- 
coming the one mile swashway, was almost wholly obliterated, and now only a 
varying diifcrencc of a few inches greater depth of water serves to indicate the 
proximity of its site. 
The eighteenth century channel is the one shown in Mackenzie's chart, and 
in order to bring the measurements to an mteUigent datum, we shall call the 
line from Old Harry to Sout h Haven the " clear line." We have seen that the 
original channel was more than three quarters of a mile east of this, and in a 
short period westcd a quarter of a mile, or more, and the process of westing 
having once commenced has gone on, and is still proceeding at a continually 
increasing rate, each successive westing bringing a decreased depth, a super- 
ficial expansion and subdivision of the currents, a Continually decreasing power 
of wash, and a rapid rolling in of the sands northerly into the bed of the re- 
maining clear channel — the prelude to a mischief worse than any other, and 
which, when it once takes place, will be utterly incurable, namely, the silting 
up of the harbour itself, precisely as has already taken place with Christchurch. 
This late or eighteenth century channel evidently had a depth of three 
fathoms, and perhaps much more. The current daily yielding to the westing 
continually became more cm-ved, and afterwards scooped out the commence- 
ment of the present entrance. The power of wash thus diverted gave up the 
channel to silting, which itself continually reacted in throwing new force into 
westing. Notwithstanding, as late as 1784; during the survey of Whitworth, 
the depth was sufficient to excite little alarm, and to leave the attention of 
improvers wholly dii'ected to the interior of the hai-bour, and the following 
year Mackenzie made his chart, giving ample proof of the state of the entrance 
then, and of its former Hne of bearing. This channel, by the Admiralty edition 
of Mackenzie, corrected by Sparke in 189.9, is shown to have been still in 
existence, and even then to have retained a depth of two fathoms. The 
entrance thus remained thirty years ago nearly half a mile east of the clear 
line, with a depth of two fathoms, and that the progress of change up to that 
time did not appear so threatening m its rapidity is evinced by the fact that 
the talented Mr. Rendle, in his surveys and plans, both antecedent and sub- 
sequent to Lieut. Sparke's survey, directed his chief attention to the interior 
of the port. 
The present channel is therefore obviously the result of agencies acting with 
such force and rapidity that in twenty years alone, between the surveys of 
Sparke and Sherrmgham, the channel had westcd half a mile. The current 
completed the excavation of its present eoui'se across Studland sands, and 
brought it within or west of the clear line, cut olf the bar from the Milkmaid 
Bank, and united it to the Hook, of which it is now become reaUy the extreme 
horn. The noble and direct channel of the eighteenth century was in this way 
converted into the one and a-half mile swashway of only six feet depth ; and 
thus the entrance to Poole harbour, once most dlreet, easy, and safe in access, 
became not a channel at all, but an expanded shallow, tortuous, difficult, and 
dangerous. 
