REVIEWS. 



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south-east midway between Old Harry and Lobster Rocks. And it appears 

 that this must have continued till nearly as late as 1700, and that if not then, 

 at least at no very remote date, that channel had a depth of above four fathoms. 

 By this date, however, the eastern cliffs had been so far abraded as to bring the 

 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 channel 

 had wested more than a quarter of a mile, and its original bed became the one 

 mile swashway, the swashway of Mackenzie, which long retained a depth nearly 

 equal to the present entrance ; and the easternmost point of the Studland 

 sands was then cut otf by the new channel, and became the point of the 

 rapidly westing Hook. Ultimately the seventeenth century channel, after be- 

 coming the one mile swashway, was almost wholly obliterated, and now only a 

 varying difference 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 intelligent datum, we shall call the 

 line from Old Harry to South 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 wested 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 roUing 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 curved, 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 directed to the interior of the harbour, and the following 

 year Mackenzie made his chart, giving ample proof of the state of the entrance 

 then, and of its former line of bearing. This channel, by the Admiralty edition 

 of Mackenzie, corrected by Sparke in 1829, 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 in 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 Sherringham, the channel had wested half a mile. The current 

 completed the excavation of its present course across Studland sands, and 

 brought it within or west of the clear line, cut off the bar from the Milkmaid 

 Bank, and united it to the Hook, of which it is now become really 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 liarbour, once most direct, easy, and safe in access, 

 became not a channel at all, but an expanded shallow, tortuous, difficult, and 

 dangerous. 



