§ 75 The Use of the Diamond-cutting Wheel.
A matter which is not very well known outside geological circles is the manipulation of the diamond-cutting wheel, and as this is often of great use in the physical laboratory, the following notes may not be out of place. I first became acquainted with the art in connection with the necessity which arose for me to make galvanometer mirrors out of fused quartz, and it was then that I discovered with surprise how difficult it is to obtain information on the point. I desire to express my indebtedness to my colleagues, Professor David and Mr. Smeeth, for the instruction they have given me. In what follows I propose to describe their practice rather than my own, which has been of a makeshift description. I will therefore select the process of cutting a slice of rock for microscopical investigation.