Ceylon moonstone is probably the best known variety of those alkali-felspars which display a prominent internal colour reflection or ‘schiller’. On account of its blue sheen and its clear transparency, the mineral has attained a certain degree of popularity and some value as a gem-stone.

The Permo-Carboniferous quartz-dolerites of central Scotland are generally holocrystalline, and only two intrusions amongst them with a fresh vitreous base have been recorded—those of Dalmeny in West Lothian, andKinkellnear Kirkintilloch (northof Glasgow). Both rocks have already been described briefly, but in view of their many interesting features a more thorough treatment seems desirable, particularly as they have a bearing on some recent theories of magmatie differentiation advanced by Dr. C. N. Fenner.

The separator here described was designed by the author some years ago in order to avoid the tedious process of hand-picking mineral powders in front of an electromagnet. It is a complete machine dealing on a laboratory scale with the less magnetic minerals, such as monazite. For research it is essential that the separation should be clean cut ; in the present case a 90% separation of glauconite from monazite can be made in a single pass, while the removal of more widely differing minerals is complete. The machine must also deal with small samples down to 0.5 gram without loss; this necessitates a small scale and slow feed ; the time required for more bulky samples is consequently rather long, but little or no attention is required during operation. Finally, all the moving parts should be of metal and easily cleaned.

The present note arises out of a paper by O. B. Bøggild, to which my attention was drawn recently, concerning the peculiar segregation of kamacite which gives rise to the Widmannstätten figures produced by etching plane sections of the octahedrite meteoric irons.

As the figures which occur in these meteorites are met with on a much smaller scale in many alloys, the structure to which they owe their origin must be of special interest to those engaged in the study of metals.