NEW ZEALAND RIVERS.

New Zealand Times, Volume XXIX, Issue 4202, 8 September 1874, Page 3

NEW ZEALAND RIVERS.

It has become a fashion with engineers and scientific men to institute.comparisons between New Zealand rivers and those of North Italy, and to assert that, in both cases, the beds of the rivers arc being steadily raised. In connection with this subject there is something said in the following paper, which was read by Dr. Ilaast at the last meeting of the Canter-, bury Philosophical Institute : —“ The wellknown Italian geologist, Comm. F. Giordano, Inspector of Mines of Italy, lately paid a visit to New Zealand, and took considerable interest in the controversy concerning the formation of the Canterbury plains. I furnished him with a copy of my printed report on the subject, but without the map and sections, of which not sufficient copies were printed off for the letter press. Since then I have been favored by Comm. Giordano with a communication dated Auckland, Aug. 2, from which I beg to lay befoi’e the Institute that portion having reference to the above-subject, which will be found full of interest. It is as follows; — l l read your paper on the formation of the Canterbury plains, aid so far as it was possible for mo to make acquaintance with the described particulars df the country without any sjiecial map and sections, I quite agree with your conclusions. ’There is almost absolute identity with a great portion of our valley of the Po, in Italy, and your conclusions are -perfectly comforraable to those of our modern geologists. I have only to observe in a subordinate way concerning the hydraulic law first announced by the Italian engineers Guglielmini, Manfredi, etc., that such laws are only suitable for rivers flowing in rather soft bottoms, while in old glacial bottoms with large boulders, and principally in hard rocks, the phenomenon is greatly altered, and implies a great duration of time. As to the case described in page 19,. viz., that the river Po, near Ferrara, raised its bed much over the surrounding country, and oven over the houses of the town, there is a mistaks, first to be ascribed to the great French engineer, Proay, who published such a statement. Really, the Po never raised its bed so high, and only a trifle in some places here and there, and near Ferrara it is still flowing with its bottom 30 feet or more below the surrounding plains. It is only the surface of the water during the floods which rises higher than the roofs of the houses, but this happens only on account of the general embankment which keeps the entire bulk- of the floods concentrated on the channel between the said embankments. What was erroneously told of the Po, by Proay firsth and repeated by others, is rather true in a branch river derived from the Reno, near Bologna, and flowing parallel to the Po, under the name of -Po di Pinaro (?). This was first an artificial river, which, having an insufficient fall, raised gradually its bed, and in places fully 30 to -10 feet above the surrounding country. But these remarks have no bearing on the general question of the Canterbury plains, which is, I think, rightly explained in your paper, 1 ”