The sample of the remarkable deposit of Diatomite, upon which the subjoined observations have been made, was forwarded to me some time ago by William Morrison, Esq., of the Academy, Dingwall, through my friend Mr John Gunn. With the exception of a brief notice in the newspapers soon after the discovery of the deposit by Mr Morrison a few months ago, and a paper entitled “On some New Localities for the Mineral Diatomite, with Notes on the Chemical Composition of the Specimens exhibited,” in the Mineralogical Magazine and Journal of the Mineralogical Society, vol. vii. No. 32, pp. 30–34, July 1886, by W. Ivison Macadam, F.C.S., F.I.C., Professor of Chemistry, New Veterinary College, Edinburgh, no statistics have been published in connection with the deposit, nor has any account hitherto been given of the Diatomaceœ which play so prominent a part in its composition.