wacke

Among these may be found in the south-west chain, masses of trap, breccia, wacke, porphyry, &c.; and in the inland parallel chain, splendid specimens of coralline schist, agate, jasper, chalcedony, amydoloid, cornelian, and silicified wood are to be met with, of which I need only raise my eyes to those collected before me to say how beautiful they are.

Yet it is by no means apparent that these alone have contributed to form the present surface, the south-eastern side of the field terminating in much older formation of wacke.

The range bordering the eastern shore of the lake is basalt and basaltic wacke; on the western, it is partly gypsum and limestone, but resting on basalt.

The wacke is of a fine grain, and its constituents are indistinctly mingled; it is traversed by empty holes and bubbles, and occasionally by druses of zeolith.

Wacke cannot resist any long exposure, and hence fluid in contact with it imbibes oxide of iron and muriate of soda; whilst flocks and herds, corrupting the element in a still more offensive manner, not only impart a fetid taste and smell, but stir up the deposited mud, which emits a volume of sulphuretted hydrogen.