. Transactions and proceedings of the New Zealand Institute . t also from the shifting ofthe river-bed, and the deposit of shingle on the adjacent lands. The townof Blenheim is situated on the middle of the plain, and unfortunately, itssite is lower by several feet than the surrounding country. Every year itsdanger is becoming more imminent, as the beds of the river and its branch,the Opawa, are gradually rising, from these rivers being compelled to depositthe drift on their banks and beds by lateral embankments. The lateProvincial Government, under the direction of eminent engineers, hastried
. Transactions and proceedings of the New Zealand Institute . t also from the shifting ofthe river-bed, and the deposit of shingle on the adjacent lands. The townof Blenheim is situated on the middle of the plain, and unfortunately, itssite is lower by several feet than the surrounding country. Every year itsdanger is becoming more imminent, as the beds of the river and its branch,the Opawa, are gradually rising, from these rivers being compelled to depositthe drift on their banks and beds by lateral embankments. The lateProvincial Government, under the direction of eminent engineers, hastried in vain many devices to direct the stream from the town. All wereunavailing, as the rapidity of the current undermined cratings, tanks, andwing-walls, while the enormous quantities of shingle deposited defied allcontrol. Not a wreck remains of all the works thus erected, costing somejei5,000. On plan No. 1 will be seen, at the point X, the lowest point inthe river bank, whence the town gets flooded by overflow, and where ths TRANS. , [■ i 9 To illuslraie vapejh/ EPMctcklii^. Macklin.—Protection of River Banks, 145 river tlireatens to form a new cliaunel, leading directly through the town, asthe lowest portion of the plain. The construction called a dam waserected some two years ago, at the point Z, (plan No. 1) and has not onlydiverted the stream into the new channel, but raised the bank of shinglebehind and below it. The old bed is gradually silting up. Had solidplanking been put in to divert the current, it would have got underminedalmost immediately, and the shingle been carried on and deposited whereit would do harm. The theorem is as follows :—If a current will carry shingle, whentravelling at the rate of six or seven miles -per hour, but will not, if thevelocity is decreased to say four, then, anything so decreasing it, will forceit to drop the shingle; and, what is of more importance, at the point whereit is so decreased. The invention I ha
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