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Under proper conditions, lamination may be produced by the same means. The result of his investigations is, that the glacier is a solid body, and that pressure answers all the requirements of the glacier-problem, and is the only thing that will. The book is one of uncommon interest, and discusses many topics beside the glaciers, though nothing that is not in some way related to them. Mr.
Above these porphyries comes a coarse, arenaceous conglomerate, the lower half white and the upper half of a pink colour, composed chiefly of pebbles of various porphyries, but with some of red sandstone and jaspery rocks. In some of the more arenaceous parts of the conglomerate, there was an oblique or current lamination; a circumstance which I did not elsewhere observe.
Slaty cleavage cannot be due to lamination, since it commonly crosses bedding planes at an angle, while these planes have been often well-nigh or quite obliterated. Examining slate with a microscope, we find that its cleavage is due to the grain of the rock.
After having fully described the obsidian, I shall return to the subject of the lamination of rocks of the trachytic series.
The sphaerulites, when not united, are generally compressed in the plane of the lamination of the mass; and in this same plane, they are often marked internally, by zones of different shades of colour, and externally by small ridges and furrows.
Yet we are not ourselves by any means devoid of 'straight lines' structurally produced, in spite of every obstacle of diversity of form and texture, of softness and hardness, of lamination or crystallisation, which are adverse to such developments.
A remarkable absence of lamination and stratification was observed almost universally in the sediment brought up from all points except where the sandy layers above alluded to occurred. Mr. Horner attributes this want of all indication of successive deposition to the extreme thinness of the film of matter which is thrown down annually on the great alluvial plain during the season of inundation.
Darwin attributes the lamination and fissile structure of volcanic rocks of the trachytic series, including some obsidians in Ascension, Mexico, and elsewhere, to their having moved when liquid in the direction of the laminae. The zones consist sometimes of layers of air-cells drawn out and lengthened in the supposed direction of the moving mass.
The strain to which the rock has been subjected has resulted in a very fine lamination, and it is considerably weathered. 9 Calcarous Sericite Schist. Seven Miles East of Seal Lake. A dark compact rock, in which calcite and sericite predominate. Quartz is less plentiful. The results of shearing and pressure are very prominent and bring out the foliation, even in the calcite.
Calcareous deposits and frondescent incrustations on the coast. Remarkable laminated beds, alternating with, and passing into, obsidian. Origin of obsidian. Lamination of volcanic rocks. The whole is volcanic, and, from the absence of proofs to the contrary, I believe of subaerial origin. The fundamental rock is everywhere of a pale colour, generally compact, and of a feldspathic nature.
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