The main portion of this memoir as far as it relates to wiltshireite was in the Editor's hands in January, 1911 ; but before it was sent by him to press I learnt that Mr. R. H. Solly had, at the Anniversary Meeting of the Mineralogical Society in 1903, described an unnamed crystal, which, from the statement made to the Society on March 21, 1911, and published in the ‘Mineralogical Magazine’ (1911, vol. xvi, p. 121), is undoubtedly the same substance as that named by me in August, 1910, wiltshireite. In the statement of March, 1911, Mr. Solly pointed out the striking relation of the crystals of wiltshireite to those of rathite ; and suggested that the latter is ohlique and not orthorhombic, as described in this Magazine (1901, vol. xiii, pp. 77-85).