The untimely death of Sir John B. Harrison on February 8, 1926, just as he was returning home after over forty-six years' service in the West Indian colonies; unfortunately prevented the publication by him of a complete account of the interesting new mineral which, as a result of much patient chemical work, he had discovered in British Guiana. As he had corresponded with me on this matter since April, 1924, and further, as this is the same mineral that I had myself erroneously described as 'allopalladium', I feel it my duty to place on record the full facts so far as can now be ascertained.

I had suggested that the new mineral might be named after Sir John Harrison, but this he objected to ; and, in consultation with the Governor of British Guiana, he proposed the name potarite (letter of April 8, 1925), but he did not himself record this name in print.

Bauxite is of twofold interest due firstly to its economic importance, and secondly to the scope it affords for scientific investigation. When these two reasons are taken into consideration, one can easily account for the enormous and rapid accumulation of literature concerning this subject. Any attempt to give a detailed account of the literature will only mean unnecessary repetition of what has been already dealt with at great length by several writers, of whom Anderson and Fox may be specially mentioned. The relation between bauxite and laterite is so intimate that a detailed study of the one is impossible without any reference to the other, and as such the description of and frequent reference to the latter should not be considered as any digression from the subject.

Experience with the usual types of glass pyknometers long ago convinced the writer that these instruments as ordinarily used are subject to considerable errors and may be quite unreliable when dealing with small quantities of material, It is true there are forms intended to be used in conjunction with a very precisely regulated water-bath which are capable of giving results of high accuracy, but this method of determination at constant temperature involves too much time and trouble for routine mineralogical work. But no matter what the design of glass pyknometers, and their variety is legion, in actual practice they suffer in common from tile defects of the material of which they are constructed.

The heavy-solution method is inconvenient ; it cannot be used for the heavier materials and there is often danger of contaminating the material which may be intended for analysis.

In the metamorphic aureole of the Falmouth. granite, the greenstones I which are largely referable to epidiorites form an important and interesting assemblage of rocks. These are lower Palaeozoic in age and are pre-granite and have suffered from metamorphism as all effect of the granite-intrusion in post-Carboniferous times.

The chief mineral constituents, viz. hornblende and plagioclase, are quite normal for a rock of this nature except that the former is clearly a derivative of augite, many relics of which are still preserved ; among the most important accessory minerals are biotite, chlorite, epidote, iron-ores, quartz, augite, axinite, and garnet. One may pass over some of the accessories as being quite usual, being partly primary and partly secondary in origin, but biotite is one of those the presence of which requires to be specially explained.