Some experiments on the hydrophane recently found in Colorado led Mr. G. F. Kunz (Am. J. Sc. XXXIV. pp. 479-480, Dec. 1887) to the extraordinary conclusion that this mineral absorbed more than its own bulk of water. Mr. Kunz, with great kindness, furnished me with a supply of this variety of opal from the locality in question. I can confirm the accuracy of his experimental results, but not of his deductions therefrom.