PROFESSIONAL work in mines during the current year has afforded me daily opportunities of studying these perforations in a variety of rocks and in varying conditions of oxidisation, depth and position.I have observed them over some distance eastward at Kalgoorlie and upwards of too miles north-westward from Coolgardie, but these notes are only intended to furnish such data as I have collected in that district wherein the " Wealth of Nations " group of mines is situated: The perforations are only noticeable where digging or other mining work brings them to light, and they are not visible in the unaltered dyke masses or rocks of a very hard character. There is no evidence to favour an idea that these rocks were very mach less oxidised when these borings were made. They appear to cover certain parallel bands, separated by short intervals, of rocks-not always dense parts or the hearts of igneous magma - and are most plentiful. in compact slates, oxidised hornblendic or kaolinized schis ts and oilier partly altered rocks. The greatest depths where they are still visible is in a shaft of the " World's Treasure " mine at seventy feet below the surface and at sixty-five feet in the " Great Eastern " mine.