Page:Transactions NZ Institute Volume 9.djvu/617

570 much like the two formations of the same name already described, but there are certain differences in its characters by which it may generally be recognized in the field; and these are, first, the perpendicularity with which it stands up in cliffs, its greater homogeneity, and a peculiar form that the fracture of the rock takes as it weathers and falls, which is conchoidal, like the fracture of flint, only on an immensely larger scale. It seems also more liable to small slips. Standing on the Purohutangihia range, and looking northwards towards the Wairoa, these beds may be distinguished from the Middle Papa (on which they rest, beyond the limits of the brown sandstone) by the enormous number of land-slips which dot the surface of the country, giving it an appearance of great barrenness: this is far from being the case, however, for whenever the soil is derived from the Papa rock, it is very rich indeed.

The quantity of material which is yearly precipitated into the beds of the streams off the surface of these Papa hills in this district is something incredible, and will ever be a constant source of heavy expense in keeping the roads open. During the heavy and continued rain of last January, many of the roads were simply impassable by horses for weeks, and many millions of tons of clay must have fallen. Some of the slips were of large extent. I saw one myself which was three-quarters of a mile long and a a quarter of a mile wide, which had slid down the side of a mountain into a gully, carrying everything before it. Large trees were uprooted and left, many of them with their heads buried deep in the ground and their roots high in the air and large Rimu trees, six feet in diameter, were broken short off in a manner that would scarcely be believed, whilst enormous masses of rock as large as cottages were piled up pell-mell on the tops of the trees. Another slip is described by one of the Surveyors as over a mile long, which fell into the Waiau River, damming up its course and causing a long narrow lake to form, three miles long.

I have already spoken of the fertility of the Papa soil. This is proved by the readiness with which the grass takes on the surface of the newly-formed slips.

Above this Upper Papa another bed of conglomerate is seen in the Esk Valley, but it is of no great extent; and above that again are a series of calcareous clays, which have a very small surface exposed horizontally, owing to the ease with which they disintegrate and are carried away by water. They are generally fossiliferous, and range upwards for about 500 feet and are then overlaid by a hard calcareous sandstone, also containing numerous fossils, the most common ones being species of Arachnoids and Placunanomia. It is this sandstone which forms the lowest strata seen at Scinde