SOME little time ago I wished to make a quartz wedge for producing interference colours with the polarising microscope. The usual wedge supplied by optical instrument makers seldom gives colours lower ...

IN very clear and simple style this book describes the outline to be followed for the complete determination of the optical characters of minerals in thin sections, with some remarks on the ...

To that rude scientist in dim historic time who first acquired the knowledge of a simple lens, how strangely must have come the wizardry of magnifying-glass. Before his wondering eyes his hand was ...