544 



NA TURE 



\April lo, 1890 



the Black Deep formerly extended in one continuous line 

 from the Kentish coast to the Long Sand Head, a distance 

 of over 30 miles. Across this chain of sands there have 

 always been shallow swatchways which communicated 

 by somewhat circuitous channels with the deep water of 

 the estuary. These are now 5 in number : (i) the Gore 

 Channel, which passes close to Margate and then across 

 the Kentish flats ; (2) the Queen's Channel, which, passing 

 between the Margate sand and Tongue sand, also leads 

 across the Kentish flats ; (3) the Prince's Channel, which 

 leads between the Tongue sand on the south side, and 

 the Shingles and Girdler sands on the north side, into 

 the Black Deep ; (4) the Alexandra Channel, which leads 

 from the Prince's Channel to the Black Deep; and (5) 

 the Duke of Edinburgh Channel, which leads from the 

 deep water of the North Sea into the Black Deep. All 

 these channels are buoyed. In the Gore Channel (some- 

 times called the South Channel), which has been in use 

 from early times, the depth at low water is 10 feet. The 

 shallow grounds shift backwards and forwards, but there 

 seems to have been always as little as 10 feet at low 

 water in some parts of this channel. In the Queen's 

 Channel, which was buoyed in the last century, the least 

 depth in passing over the Kentish flats is 13 to 14 feet at 

 low water. In Prince's Channel, which was buoyed in 

 1846, and lighted in 1848, the least depth is 20 feet at 

 low water, but theie is a patch of 17 feet at its western 

 end in the centre of the channel which seems to be 

 always in this channel though not always in the same 

 position. It is shown by Bullock in 1839, by Calver 

 in 1862, and by the Triton in 1880. The Alexandra 

 Channel, which is a swatchway between the Shingles and 

 Girdler sands, had no existence in 1800, the Girdler and 

 Shingles forming with the Long Sand a continuous chain 

 at that date. In Bullock's survey of 1839, the Alexandra 

 is shown as a blind inlet on the north side of the Prince's 

 Channel, which was cut off from the Black Deep by a 

 ridge over which the depth was 7 feet at low water. 

 When surveyed by Calver in 1862, the least depth in the 

 channel was 20 feet ; and when. surveyed by the Triton in 

 1888, the least depth was 23 feet. It is, however, much 

 narrower now than in 1862, and if it continues to decrease 

 in width will not be available for traffic, as there is not 

 now much more than room for two large vessels to pass 

 each other, and bad steerage might cause an accident. 



Of the Duke of Edinburgh Channel, which is a broad 

 swatchway at present dividing the Long Sand from the 

 Shingles Sand, we have a tolerably complete history ; and 

 as this would seem to be a channel which opens and 

 closes periodically, Plan III. has been constructed to show 

 its condition each time it has been -surveyed. The first 

 record we have of it is on an old chart of 1794, when it is 

 shown as a 9-feet swatchway, and is named " Smugglers' 

 swatch." When surveyed by Thomas, in 18 10, it was 

 named "Thomas's New Channel," and there was then a 

 narrow passage carrying 30 feet at low water between the 

 Long Sand and Shingles. In 1839, when surveyed by 

 Bullock, and named " Bullock Channel," this 30-feet 

 swatchway of Thomas s was obstructed by a bank in the 

 middle, which dried at its north end, leaving a passage of 

 15 feet on its east side, and a very narrow gat of 25 feet 

 on its west side, but one mile farther west a new channel 

 was opening out, the shoalest water in which was 16 feet. 

 This appears as an inlet into the sand-bank on Thomas's 

 chart. 



The next time it was surveyed was by Calver, in 1862, at 

 which date Thomas's Channel had closed completely, but 

 the channel west of it had opened out and become a wide 

 deep-water swatchway, the least depth in which was 42 

 feet at low water. Early in 1882 it was thought advisable 

 to buoy this channel, and the Triton was ordered to ex- 

 amine it, when a 30-feet patch was discovered near its 

 centre. In the autumn of 1887, this patch was reported 

 to have shoaled ; and in 1 888, when examined again by the 



Triton, it was found to be upwards of a mile in length 

 with 22 feet on it. In October 1889, the channel was 

 again examined, when the least depth on the central 

 patch was found to be 21 feet, and it had a tendency 

 to shallow to the eastward. The channel was buoyed in 

 the summer of 1882, and re-named by the Elder Brethren 

 of the Trinity House " Duke of Edinburgh," after the 

 Master of the Trinity House. It was lighted in December 

 1889. 



The various surveys seem to show that the estuary 

 has a tendency for the most part to return to the con- 

 dition it was in about 1800. In that year there were 

 no deep-water swatchways across the banks, and the 

 channels that opened up subsequently seem now to be 

 all closing again. At any rate, those in use as ship' 

 channels evidently will require constant watching. 



Should the Duke of Edinburgh Channel close, and none 

 other open out, it will materially interfere with the heavy 

 traffic into the estuary from the southward, for it will 

 necessitate either waiting for high water or passing round 

 outside into the Black or Barrow Deeps, which will have to 

 be buoyed and lighted to make them readily accessible. 



There is one other shoal, the '' Kentish Knock," which 

 may be said to belong to the estuary. This is a sand- 

 bank about 6 miles in length and 2 in breadth, on the 

 south-east side of the outer part of the Long Sand. Its 

 shape and area, within the contour-line of five fathoms, 

 would appear to be fairly constant ; but it had a swatch- 

 way across the north end, when surveyed by Calver in 

 1864, which has now entirely disappeared. Between the 

 Kentish Knock and Long Sands is a channel, two miles- 

 wide, named the Knock Deep. At the north end of this 

 channel the soundings arc much shoaler than when 

 surveyed by Bullock. In some cases the difference is as 

 much as 12 feet. 



Although the general tendency of the banks in the 

 estuary seems to be to revert to the condition they were 

 in about the year 1800, it is not possible to predict that 

 this will certainly be the cise. If, as seems probable, the 

 condition of the estuary is due to the action of the sea 

 in casting up banks, and of the tidal flow in cutting 

 channels through the banks thus formed, it is evident that 

 much will depend on prevailing types of gales. There 

 can, however, hardly be a doubt that any diminution of 

 the volume of the water running into and out of the 

 estuary would diminish its power of making deep-water 

 channels, so that any action tending to decrease the flow 

 into and out of the various rivers should be avoided if 

 possible ; as although it is conceivable that a given type 

 of strong winds, extending over a lengthened period, 

 might have the effect of closing the various swatchways 

 across the banks, it does not follow that a cessation of 

 these winds would cause the channels to be again opened 

 out if the volume of the tidal flow was seriously 

 diminished. T. H. Tizard. 



NOTES. 

 The respect in which science is held in France was once more 

 exhibited in a very striking way at Saint Sulpice, Paris, on Tues- 

 day, in connection with the funeral service of M. Hebert, Professor 

 of Geology, member of the Institute, and honorary doyen of the 

 Faculty of Sciences. Deputations from the Institute and Faculty 

 of Sciences were present, and the Paris correspondent of the 

 Times says ihat all the great scientific and literary institutions 

 of Paris were represented. At the cemetery of Montparnasse, 

 where the interment took place, speeches were delivered by M. 

 Gardry, in the name of the Institute ; M. Darboux, in the name 

 of the Faculty of Sciences ; M. Marcel Bertrand, in the name 

 of the Geological Society ; M. Jannery, in the name of the 

 Normal School ; and M. Bergeron, in the name of the old 

 pupils of M. Hebert. 



