A FLOATING BREAKWATER.

Press, Volume XII, Issue 1582, 2 December 1867, Page 3

A FLOATING BREAKWATER.

The following novel suggestion was recently communicated by Dr. Dowuing to the Town Council of Brighton, by whom it was considered so important that they directed it to be published:—

In the course of my travels in different parts of the world I have often had occasion to notice the devastating effects of the ocean upon even the boldest and most rocky shores, and the great immunity enjoyed by certain portions when protected by a natural rich growth of that species of sea-weed denominated kelp. This is the macrocystis pyrifera of botanists, and rises by long, cord-like, and tough stems from the rocky bed beneath, and extends great spreading fronds or leaves over the surface of the water. Through these the boisterous waves force their way slowly and as it were painfully, until, if the bed of weed be thick, their force is gradually but surely broken, so that they reach the coast with such gentle ripple as is quite contrasted with their headlong fury on adjacent parts. These effects may; be observed sufficiently on our shoi-es, more especially on the west coast of Scotland and the north and west of Ireland; But nowhere, perhaps, are they so well illustrated as on the southern extremity of the great continent of America, on the western shores of Chili, Patagonia, and Terra del Fuego. For.here, as is well-known, Neptune and Boreas hold undisputed sway. Terrific gales blow almost continuously from the westward, so that round the Horn ■ from the east, under canvas alone, is at all times extremely difficult, at certain seasons nearly impossible. A glance at the map of South America would demoustrate the effects of these violent gusts of wind. They have roused the ocean to such persistent washing of the land in one direction as to have apparently bent the extremity of the continent to their will, and rounded off every salient obstacle to their fury.

And it is here, where the encroachment of the water upon the land-i&tfae most apparent, that the 'guardian influence of the kelp is the most capable of demonstration.

My attention may have been originally directed to the subject by the casual observations of master mariners, or from the perusal of the works of the most celebrated navigators; but the following passage in the journal of Mr Darwin, the naturalist, now worldfamous from his work on the " Origin of Species," struck mc as embodying all that is needed in the way of collateral evidence. Sailing with the late lamented Admiral, then Captain Fitzroy, through the Straits of Magellan into the Pacific, he says, " There is one marine production from its importance, is worthy of a particular history. It is or Macrocystis pijrifera. This plant grows on every rock, from low-water mark to a great depth, both on the outer coast and within the channels. I believe, during the voyages of the Adventure and Beagle, not one .rock near the surface was discovered which was not buoyed by this floating weed. The great I service it thus affords to vessels navigating near this stormy land is evident, and it certainly has saved many a one from being wrecked. 1 know few things more surprising than to see this plant growing and flourishing amidst those breakers of the Western ocean, which no mass of rock, let it be ever so hard, can long resist. The stem is round, slimy, and smooth, and seldom has a diameter of so much as an inch. A few talten together are sufficiently strong to support thej weight of the large loose stones to which in the inland channels they, grow attached, and yet some of those stones were so heavy that when drawn to the surface they could scarcely be lifted | into the boat by one person. Captain Cook, in his second voyage, says that " this plant at Kerguelen Land rises from a greater depth than twenty-four fathoms, and as it does not grow in a perpendicular direction, but makes a very acute angle with the bottom, and much of it afterwards spreads many fathoms on the surface of the sea, I am well warranted to say that some of it grows to the length of sixty fathoms and upwards." I do not suppose the stems of any other plant attain so great a length as 360 feet, as stated by Captain Cook. Captain Pitzroy, moreover, found it growing up from the greater depth of forty-five fathoms. Mr Darwin finally adds—" The beds of this sea-iceed, even vflien of not great breadth, make excellent natural floating

h:eakwaters.-Itis quite curious to see in an exposed harbour (he is writing now of the western coasts of Patagonia and Terra del Fuego) Tioic soon the waves from the open sea, as they travel through the open stems, sink in height and pass into smooth wafer. ,.

Here then is a distmefc statement made by an acute observer, and doubtless verified by his chief, whom I sincerely wish were here to support it, that ? a bed of kelp, even of moderate diameter, has the power of cheeking the violence of waves impelled by the most furious galea on to a rocky shore, and gradually but surely lulling them to peace. The linn, in fact, tamed and made gentle as a lamb

Assumiug, therefore, this power of the sea-weed, let us now endeavour to utilize the fact. As a preliminary,let mc state at once that I have no intentions of recommending the laying down extensive beds of kelp in front of a gay town like Brighton, even were it practicable. They would be unsightly, some would think insalubrious, and they certainly would not improve it as a fashionable bathing locality. Again, although there would be no difficulty in collecting the plants in almost any quantity, and with great length of stem, yet unless the sea-bed were rocky, which is not the case in the desired localities, they would have no sufficient holding ground, and could not be cultivated to advantage. In fact, the idea of such a proceeding, in the present state of our knowledge, may be considered Utopian, and should be rejected altogether.

Yet man generally succeeds best in his efforts at improvement when he follows, as closely as he can, the footsteps of his Maker ; my proposition is, therefore, that we here take advantage of the lesson afforded by nature, and endeavour to imitate her works. She shows us a natural floating breakwater. Let us construct an artificial one on the same plan.

I propose that a series of rings, fixed on the end of piles or otherwise, be firmly secured to the ocean-bed in rows parallel to the shore, and at some distance outwards from low-water mark. To each of theee stout ropes should be attached, which might branch off into lesser ones until they ended in cords, say of half-inch diameter, and of such length as to reach the surface at a very acute angle with the bottom. This should be made as light and durable as possible, as they would represent the stems of the macrocy&fls pyrifera. The lengthy and buoyant fronds of the sea-weed would be imitated by small floats made of wood, cork, or other material, and not more that 2ft 6in in length. They may be oblong or oval, well rounded .off, and: either single or linked together in a short series. Their shape is not of importance, but I consider it essential that they be flat and of merely sufficient lightness to buoy up the cordage. If properly fixed these disks would in calm weather float side by side, almost level with the water, and nearly cover its surface. During gales the first disks would, I imagine, be submerged more or lees, and thus offer a greater resistance to the water. Indeed, we' could scarcely put a limit to this power if the lines were sufficiently approximated and buoyed at short intervals beneath the surface with pieces of cork. This is so obvious that I think one of the best arrangements would be that of small ropes, sustained by disks of cork, placed at short intervals, like the papers on the tail of a boy's kite. Experience, therefore, must determine how thickly and broadly the floats should be moored, but doubtless they must extend several fathoms outwards from the shore, in order to subdue effectually the momentum caused by our south-west gales. There would be much wear and tear of the tackle, doubtless, but I imagine there would be no difficulty in renewing it when necessary, as well as driving the mooring piles, in these days of engineering skill.

This apparatus, subject to the modifications and improvements that will be suggested by men of science and experience, I respectfully submit to the consideration of the Town Council of Brighton, under the title of " The Comminuted Floating Breakwater." Qf course it could be applied to any part of the coast, but, for the sake of experiment, to none better perhaps than opposite the King's road and about as far out as the Pier head. Here, from the summit, say, of the Grand hotel, good observations might be taken of tho way it behaves during rough weather. It would not be unsightly, and rather an advantage than otherwise to bathers, especially if they could swim. Lastly, although offering an effectual barrier against mountain waves and a secure' harbour of refuge for boats, it tvould not in the slightest degree impede navigation, as craft even of the smallest tonnage could sail freely over it and get at once into smooth water. The only exception to this would be in the case of steam vessels, the wheels or screws of which might become hampered by the floats. But as due channels would be provided, little inconvenience would result from this cause. "Any further explanation will be cheerfully afforded. Let mc add that the few friends (chiefly nautical men) to whom I have mentioned this novel kind of breakwater have been equally sanguine as myself as to its success. " C. Togood Dowsing; M.D., "Author of the ' Eanqui in China;' "And other works."