much more basic than any of the preceding rocks. It is heavy and black, with all the appearance of a basalt, and shows microscopic olivine. It contains, however, felspar and augite crystals like the porphyritic crystals in the augite andesites previously described. They are not very abundant, and to them are added olivine in numerous crystals, and felspar laths. The groundmass is in the main crystallitic, but shows far more crystalline particles between crossed nicols, and glass is scarcely visible. The rock thus shows a relationship to the augite andesites, but at the same time approximates to the basalts. Another variety collected by Mr. Cussen contains chiefly olivine among the larger crystals, though a few smaller augites are present. The groundmass is partly crystallitic, but contains very numerous felspar laths. The analysis of the former variety by Mr. Pond shows (see No. 3) that it contains 52·1 per cent. of silica—an amount considerably higher than that usually present in rocks recognised as augite-andesites. Its specific gravity is 2·94, which also indicates a rock more basic than ordinary augite-andesites. The magnesia and lime are also present in much higher proportion than in the other rocks of Tongariro. Rosenbusch, in his last edition,* “Physiographic der Massigen Gesteine,” p. 702. states that the augite-andesites seldom contain less than 56 per cent. of silica, whilst some basalts attain the same percentage. Teall quotes twenty-three analyses of porphyrites and andesites as varying between 66·75 and 54·73 per cent, of silica, whilst the same number of basalts showed percentages of silica varying between 53·73 and 42·65.† “British Petrography,” p. 49. Under the circumstances, we shall probably be justified in terming the rock a basalt, though we must admit that it is closely related to the augite-andesites. The system of classification of rocks is necessarily more or less arbitrary, and the present rock is one which lies near the line of division between the augite-andesites and the basalts. Pumice on Tongariro.—We have referred above to the popular idea that the great quantities of pumice around Lake Taupo are derived from Tongariro and Ruapehu, and have stated that the examination of the country to the south of Lake Taupo lends little support to any such theory. Pumice is indeed found on Tongariro, but in comparatively small quantity. A small amount of pumice of an acid character, containing 75·25 per cent. of silica (see analysis No. 6), was found in the North Crater of Tongariro, and one or two small fragments of rhyolites were found elsewhere on the mountain-top. But with these exceptions all the rocks high up on the mountain were of a more basic character. On the lower