Page:Quarterly Journal of the Geological Society of London, vol. 26.djvu/259

1869.] the bole have been ejected in rapid succession, the decomposition of the intervening volcanic flow being subsequent to the eruption of the superimposed rock; or, in cases where the bole has been indurated, if such do occur, the decomposition of the original rock was effected before the subsequent volcanic outburst ; but as these effects were limited to simple induration, except in the case of the production of the pisolitic iron-ore, hereafter to be mentioned, it is extremely probable that these eruptions were subaqueous.

3. Absence of Boles above the horizon of the Iron-ore. — Though boles and lithomarges unaccompanied by an iron-ore occur below the iron-ore series, yet no such beds have been met with above the pisolitic ore, though many hundred feet of basalt have been examined.

Fig. 2. — Section of Galboly Mountain.

1, 2, 3, 4, 5. Beds of bole and lithomarge.

a. Pisolitic iron-ore. H C. Hard chalk.

On the face of the Galboly mountain three hundred feet of basalt intervene between the pisolitic ore and the White Limestone ; and four masses of lithomarge and bole are seen within that thickness, underlying different basaltic terraces (see fig. 2). A similar interstratification is also seen at Slievananee, below the section given at p. 153.

The section of Cape Pleaskin presents five thin strata of ochre below the iron-band, and unassociated with iron-ore, in the lower 180 feet ; while that portion of the basaltic escarpment (of the thickness of 172 feet) above the iron stratum does not exhibit a single ochre-bed.

A section at Carnowry, Rock Head, given by Portlock*, shows three thin beds of ochre or bole in a thickness of basalt above the


 * Loc. cit. p. 142.