the breccia are not fused at the edges. The eruptive force was probably steam or water-gas, acting under great pressure, but at no high temperature. According to Mr. Dunn, in the Kimberley Mine, at a depth of 120 feet, several small fresh-water shells were discovered in what appeared to be undisturbed material.
A selection of thin sections of some of these rocks and minerals, mounted as microscopic objects and viewed by polarised light, are not only of interest to the geologist, but are objects of great beauty.
The appearance of shale and fragments of other rocks testify that the melange has suffered no great heat in its present condition, and that it has been erupted from great depths by the agency of water vapour or some similar gas.
The rock outside the pipes and encasing them is called " reef." Inside some of the mines occur large masses of " floating reef," covering an area of several thousand
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