The great variation which occurs in the specific gravity of zircons seems to render it possible that the presence of fluid and gas inclusions might, to some extent, account for this. A small, partly red, partly eolourless crystal was selected from a number of others all derived from the Riou Pezzoliou, Expailly, near Le Puy, which, when examined under the microscope, was found to contain numerous inclusions, some with, others without bubbles.