The crystallization of silica from fused metals, although at first sight appearing to be of little importance, nevertheless presents some features of peculiar interest. It also constitutes a field almost entirely new to the investigator, though the subject is one which, from a technical point of view, may prove to be of very considerable importance.

I have therefore undertaken the examination of some of the facts relating to this subject—at first more particularly inquiring into the nature of the change which occurs when silica itself is kept at a high temperature for a number of hours and subsequently submitted to a process of very slow cooling.