TIMARU HARBOR WORKS.

Globe, Volume XX, Issue 1644, 28 May 1879, Page 3

TIMARU HARBOR WORKS.

The progress of the harbor works (says the " Timaru Herald ") has already produced a very marked chango on the beach—an effoct which time will but render more marked. The breakwater is now extended so far seaward that the northward travel of the shingle is completely arrested at this point, and in consequence of the effectual damming of the Btream, a largo quantity of shingle haß accumulated on the south side of the works. While the tendency of the surf to carry the looso material of the beach northward remained a theory, that tendency was denied and ridiculed on nearly all sides, and in all terms j but thoße who most strongly opposed the theory must be convinced by the demonstration afforded by the growth of the Bhingle bank opposite the railway station. As far as the harbor works are concerned tho accumulation of shingle must be considered as eminently advantageous. In '■the course of a few years, judging from the rate at which the growth of the bank has proceeded up to tho present, a considerable area of land will be reclaimed by tho action of the sea itself, which will have a double value as being a highly marketable property, and as affording, so far as it extends seaward, a most efficient projection to the breakwater itself. We are not yet in a position to judge of the avorage rate at which the bank may be expected to increase. It is the southerly seas that have the most power in bringing material northwards, and there have been none such since the breakwater has been so far extended that

the waves cannot carry shingle nor sand round it. At the time of the last southerly seas a large quantity found its way round the works. Under the most advantageous circumstances, however, the future growth of the bank will apparently be leea r.apid than at present, inasmuch as, tha angle formed by the breakwater with the beach becoming loss and \es% acute, the materials deposited will bo spread over increasing lengths of beach. The growth of the bank will soon be found to entail inconvenience on the southern landing services—in fact, the G-oorge street Service is already suffering inconvenience—and it will, soonor or later, be found necessary for tbeir proprietors to take up a working ground nearer the sea. Possibly such, a shifting of their base cf operations will b« required more than once or twice before tha completion of the breakwater nhali retirler their operations obsolete. Not less interesting, except from a. commercial point of view, than the growth of the shingle hank is the conslant process of destruction to which it is subjected. Many persons must havo notod that the shingle on wb/ch the surf now beats, near tho breakwater, contains a far larger proportion of whitd or light-coloured pohb'.ea than tho Bhingle higher up on the beach. The explanation of thia in that in the ceaseless weijr and tea'* to which the material is subjected, tho softer stones are rapidly destroyed, being ground into an impalpable mud, which the recoding waves carry out to sea and deposit \n the still depths. Thorn is no doubt that tho " good holding ground " of the Tiraaru roadstead is oamposect of mud derived from the attrition of tho shingle on the neighbouring beach. Tho white and light-coloured pebbl s are of quirt z or of othor substances belt3r able to withstand the grinding action, the

shingle is subjected to. Succumbing, therefore, more slowly to that action than the darker and aofter pebbles, they will gradually, according to the Darwinian law of " survival of the fittest," como to form larger and larger proportions of the whole. Ultimately, the result of this process of " natural selection " will be that near the breakwater itself the pebbles and eand will bo almost wholly of quartz or similarly hard substance, as_ is the case at the present extremities of this long shingle beach—at Oamaru and at Bank's Peninsula.