Page:Quarterly Journal of the Geological Society of London, vol. 26.djvu/263

1869.] thickness in the same direction. Wherever a fine sediment occurs, even though in the conglomerate, plant-remains are present.

The plant-layer, which is mined and used as a flux, is of low specific gravity, and is not sufficiently rich in iron to be valuable for smelting. The following analysis of this rock is communicated by Dr. J. Apjohn.

Water 25.78

Silica with a little alumina 36.40

Peroxide of iron 9.12

Alumina and other oxides (by difference) 28.70

100.00

Percentage of metallic iron 6.36

In a neighbouring pit on the N.E. side of the line of railway there is exhibited a similar section. The conglomerate-bed presents a maximum thickness of 10 feet, thinning away to the N.E., and with the underlying shales dipping in the contrary direction. The shales are about 6 feet thick and are underlain by lignite, which surmounts an amygdaloidal basalt.

2. Relation of the Strata to the Basalts. — The railway- cutting about a quarter of a mile to the N.E. of the ochre-pits presents a section (fig. 4), which enabled us to place the fore-mentioned sedimentary ores, shales, and lignite in juxtaposition with a subsequent basaltic flow (1).

Fig. 4. — Section in Ballypalidy Railway-cutting, north side. A thin band of impure lignite (3), with or without a clay band below containing plant-remains, and always accompanied by an overlying stratum of clay (2), is seen in one place following the undulating line of the upper surface of a concretionary basalt (4), which latter is superimposed upon a ferruginous series of iron-ore and the underlying bole (5) and lithomarge (6). Elsewhere the basalt above the pisolitic iron has been eroded, and the lignite series rests upon the pisolitic iron-ore or inferior basalt.

The continuity of the lignite-band of these sections with that of the underlying plant-beds and conglomerates in the pits some little distance to the west, is not traceable step by step ; but there is little doubt that the several portions visible are parts of one stratum.