proceedings: geological society 517 



rated with calcite, precipitation must take place, independent of any 

 other agencies, wherever the water is being warmed, or is losing free 

 C0 2 , or both. This view that this mode of precipitation, brought about 

 by the operation of purely inorganic factors, actually takes place on a 

 large scale, does not exclude the other views which have been pro- 

 posed to account for the deposition of limestones, and is not in conflict 

 with any facts which are definitely ascertained. It could be estab- 

 lished or disproved by systematic bathymetrical and chemical investi- 

 gation of the ocean, an investigation which would have an important 

 bearing on many biological as well as geological processes. 



H. E. Merwin: The forms of calcium carbonate and their occurrence. 

 A new form of calcium carbonate which is hexagonal, optically positive, 

 and less stable than aragonite, was described. It forms readily in solu- 

 tion at about 60°. Criteria for distinguishing the three established 

 forms of calcium carbonate were discussed, and the necessity for dis- 

 tinguishing the properties of aggregates from those of definitely bounded 

 crystal fragments was emphasized in connection with evidence which 

 was given to show that "vaterite" is really porous calcite and that 

 "ktypeite" is porous aragonite. The precipitation of aragonite is 

 favored by the presence of sulphate, but magnesium has little influence. 

 Sulphate is taken into solid solution in aragonite in sufficient quantity 

 to make it more stable probably than calcite. Aragonite containing 

 sulphate was separated from muds of the shoal waters of the Bahamas. 

 Four types of original structure of oolites were described and illus- 

 trated. 



Discussion led by T. Wayland Vaughan, Chas. D. Walcott, G. R. 

 Mansfield. 



The 310th meeting was held in the lecture room of the Cosmos Club 

 on May 10, 1916. 



informal communications 



Fred. E. Wright described a more delicate method than those usu- 

 ally employed for determining isotropic and anisotropic character in 

 opaque minerals. 



REGULAR PROGRAM 



Henry S. Washington : The persistence of the volcanic vents at Strom- 

 boli. When Stromboli was visited in August, 1914, it was in a state 

 of moderate activuy, there being five vents on the crater terrace. The 

 most active of these, that at the east end of the upper edge of the 

 Sciarra, is called 'Tantico," and Bergeat pointed out in 1899 that this 

 vent had probably occupied the same location for over a hundred 

 years. Search through the literature yielded evidence, especially in 

 the form of sketches and plans of the crater terrace, favoring Bergeat's 

 view, and going to show that not only this vent, but also another on 

 the west, scarcely less active in 1914, have not materially altered their 



