The January number of this Magazine contains an interesting paper on a soda-bearing rock from Dinas Head, Cornwall, read by Mr. Howard Fox, F.G.S., at the Oxford meeting of the British Association. Mr. J. J. Harris Teall, F.R.S., supplied notes on the microscopic structure of some of the specimens; and four chemical analyses by Mr. J. Hort Player and Mr. Arthur F. Hosking are given in the paper, from which it appears that the specimens analysed are composed of from 64 to 66 per cent of silica; from 19 to 20 per cent. of alumina; 9.8 of soda; and small amounts (generally under 1 per cent.) of potash, titanic acid, ferric and ferrous oxides, magnesia and lime.