proceedings: geological society 501 



ordinary gravel, and resonating space of approximately uniform "mesh" 

 will be provided. Field observation shows that it is also essential 

 that the pebbles be of fine-grained dense rock and smoothly rounded, 

 so that the rubbing of one upon another will tend to set up definite 

 vibrations rather than irregular jars, and shows further that the coarser 

 the material of a "singing" beach the lower the note produced. If 

 this suggested explanation be correct, shingle should be defined as 

 "beach material, coarser than sand, consisting of smoothl}^ rounded 

 pebbles of dense, fine-grained rock, of approximately the same size, 

 and hence not having the interstices filled with finer material, which 

 gives out a sound resembling a musical note, when trod upon or when 

 rolled about by waves." 



Mr. Frank L. Hess said that tourmaline cobalt-bearing veins oc- 

 curring in the Blackbird region, Lemhi County, Idaho, are dense 

 black and occur in a dark, fine-grained, thin-bedded quartzite. The 

 cobalt is in many places difficult to see, but it shows up on crushing 

 and panning the rock. A polished section was exhibited showing a 

 mass of microscopic tourmaline crystals with clouds of included cobalt 

 minerals, mostly cobaltite. 



Dr. H. M. Ami called attention to the fact that on the shores of the 

 Dead Sea in Palestine there are innumerable fresh water shells washed 

 up by the waves along with drift wood and other forms of vegetable 

 matter. The hypersahnity of the water precludes any form of life. 

 He surmises that these shells presumably are brought into the sea by 

 Jordan River, and calls attention to the fact that the presence of 

 freshwater shells in strata does not necessarily predicate that the water 

 in which the sediments were laid down was fresh. 



Regular Program 



E. W. Shaw: Present tendencies in Geology. III. Stratigraphy. 



(This paper will be published later in this Journal.) 



M. I. Goldman: General character, mode of occurrence, and origin 

 of glauconite. 



The characters of the mineral were briefly reviewed, and it was 

 pointed out that there are a number of varieties in addition to the 

 common form in rounded, compound-polarizing grains. Some of these 

 seem to have been deposited epigenetically from solution, but the 

 speaker did not believe that there is good evidence for the deposition 

 of any of them from solution syngenetically. The importance of fur- 

 ther study, especially chemically, of the well defined, micaceous green 

 crystals sometimes found associated with the cryptocrystalline forms 

 of glauconite, and believed to be glauconite, was emphasized. 



The chemical composition and mineralogical affinities were dis- 

 cussed. The potassium content, which averages around 7 per cent, 

 distinctly differentiates glauconite from the chlorites which it resem- 

 bles in many of its mineralogical characters, and the predominance of 



