On the petrography of the silurian shales from Hadeland, Norway.

By means of microscope, X-ray, and D.T.A., constituents of the Silurian shales from Hadeland are determined to be: quartz, calcite, mica, chlorite and illite. Some chemical data are given, together with suggestions concerning the low phosphorous-content and the high manganese- and MgO-content in the same shales. The problem of red colour in shales from stage 7c is discussed briefly, as is an occurrence of speckled shale in the same stage.