Part 360

In passing along we crossed the hills Vungue or Mvungwe, which we found to be composed of various eruptive rocks. At one part we have breccia of altered marl or slate in quartz, and various amygdaloids. It is curious to observe the different forms which silica assumes. We have it in claystone porphyry here, in minute round globules, no larger than turnip-seed, dotted thickly over the matrix; or crystallized round the walls of cavities, once filled with air or other elastic fluid; or it may appear in similar cavities as tufts of yellow asbestos, or as red, yellow, or green crystals, or in laminae so arranged as to appear like fossil wood. Vungue forms the watershed between those sand rivulets which run to the N.E., and others which flow southward, as the Kapopo, Ue, and Due, which run into the Luia.