Geological Society. 45$ 



undetermined, nothing appearing in the analyses to account 

 for it. It was thought that colloidal metals might in some 

 cases be concerned ; and if ultra-violet transparency were 

 found, this would be considerable evidence for such a view. 

 It has been found that the variety of zircon called hyacinth 

 only begins to be opaque at X2617, and one variety of yellow 

 topaz at A, 2294. In these cases the presumption is strong 

 that the colouring matter is of the nature of a colloidal metal. 

 The extreme ultra-violet transparency of the solution of 

 magnesium in ammonia confirms the view that these metallic 

 solutions are to be regarded as colloidal. 



The author desires to acknowledge his gratitude to 

 Professor the Hon. R. J. Struti, F.R S., for suggesting 

 the work, and for continuous interest and advice. 



Physics Department, 

 Imperial College of Science and 

 Technology, S.W. 



XLTII. Proceedings of Learned Societies. 



GEOLOGICAL SOCIETY. 

 [Continued from p. 296.] 



January 24th, 1917.— Dr. Alfred Harker, F.R.S., President, 

 in the Chair. 



Mr. Scoeesbt Rotjtledge, M.A., gave an account of Easter 

 Island. He said that the Expedition, that he had had the 

 honour to command, was organized with the object of carrying 

 out a long-standing wish of various bodies interested in anthro- 

 pology. This wish was that Easter Island, and other islands most 

 near to it, though far distant from it, should be thoroughly 

 examined, and that all information and material thereon found 

 should be carefully considered on the spot, or, if possible, be brought 

 back for comparative study. 



This programme necessitated a vessel being specially designed, 

 built, and equipped for the purpose. A schooner with auxiliary 

 motor power, the ' Mana,' of 90 tons gross register, 78 feet 

 on the water-line, 20 feet beam, and drawing 10 - o feet aft, 

 was accordingly completed by the end of 1912, and she sailed 

 from Southampton in February 1913 with a company of twelve 

 all told, of whom four formed the scientific staff. After the 

 longest voyage ever made by a yacht under canvas, she sailed 

 into Southampton again in June 1916, without having experienced 

 accident to man or material. 



The course taken was through the Magellan Straits, and thence 

 through the labyrinth of Andean waterways that stretch north 

 therefrom, and are known as the Patagonian Channels. 



On reaching Juan Fernandez Island, the ' Mana ' had to put 

 back to Valparaiso because the geologist of the Expedition, the 

 late Mr. F. L. Corry, had contracted typhoid fever on the Chilean 

 coast. Mr. Corry never recovered sufficiently to allow him to 



