Januaey 10, 1896.] 



SCIENCE. 



49 



States, stated tliat in his travels in the 

 West Indies he had found no pumiceous 

 rocks among the volcanoes, and suggested 

 the possibility of remoter sources. C. W. 

 Hayes remarked upon a vast formation of 

 volcanic tuflfs met by him in eastern Alaska, 

 extending over many hundreds of square 

 miles and up to 75 feet thick. Its bulk he 

 estimated at over 100 cubic miles. He also 

 referred to the top layer of the Devonian 

 rocks of the southern Appalachians, which. 

 8 inches to IS inches thick, extends from 

 eastern Tennessee and Georgia to Arkansas 

 and Missouri, and which is regarded as a 

 volcanic tuff. L. V. Pirsson mentioned 

 the wide area over which the iine eject- 

 ments of Krakatoa had spread and gave a 

 brief sketch of Backstrom's observations on 

 the presence of volcanic dust in the sea 

 beaches of Norway. Much of this is de- 

 monstrably from Iceland, but other samples 

 agree with the products of no volcano in 

 the Atlantic basin. Caution is needed not 

 to be misled by artificial slags and cinders. 

 M. E. Wadsworth cited the tuffs collected 

 by S. Garman, G. P. Merrill and J. S. 

 Diller in Nebraska, and by Diller in Massa- 

 chusetts. Persifor Fraser called to mind 

 the dust that was gathered by Joseph 

 Wharton in Philadelphia on the first snow- 

 fall, December, 1883, Krakatoa having been 

 active in August of the same year. Its 

 microscopic characters agreed entirely with 

 samples from Krakatoa. 



The discussion then took up the length of 

 time, during which such dust might remain 

 suspended in the atmosphere. W. M. 

 Davis stated that the peculiar red sunsets 

 following the Krakatoa outbreak lasted 

 through 1884, and that the so-called 

 Bishop's ring was visible around the sun 

 for fully two years . N. S . Shaler mentioned 

 the observations of the Germans on shining 

 clouds that were at first 80 miles in the air 

 and that were later noted at. 140 miles before 

 they disappeared. He also reminded the So- 



ciety that the same red sunsets followed the 

 great eruption of Skaptar Jokul in 1783. 

 C. H. Hitchcock raised the point that red 

 glows from aqueous vapor should not be 

 confused with colors fi'om volcanic dust, as 

 the latter are chiefly greenish, but in reply 

 it was brought out that the colors were due 

 to diffraction and that the reds might also be 

 caused by fine particles of mineral matter. 



A needed term in Petrography. L. V. Pies- 

 son, New Haven, Conn. 

 The speaker adopted the definition of a 

 crystal that is based upon its outer plane 

 faces, rejecting thus the tendency of some 

 authors to make it dependent on internal, 

 physical and optical i)roperties. He then 

 spoke of the inaccuracy of using the word 

 crystal for the mineral components of a 

 rock, which, in most cases, have no plane 

 faces, illustrating his point by the augites 

 of augitic rocks. For such the terms crystal 

 fii-agment and crystalloid had been used, but 

 were both objectionable. Therefore, after 

 consultation with E. S. Dana, he proposed 

 the name anhedrine for them, the word 

 meaning without planes. In a brief dis- 

 cussion that followed, the term was on the 

 whole well received, although the general 

 feeling was strong against the introduction 

 of further new terms into the over-burdened 

 nomenclature of petrography and other 

 branches. 



Note on the Outline of Cape Cod. W. M. 



Davis, Cambridge, Mass. 



The speaker described the topography of 

 the Cape from a point some distance south 

 of Highland Lighthouse, to the north, and 

 made a distinction between the ' mainland 

 outline ' or the original glacial drift hills of 

 the highlands, and the ' constructional out- 

 line ' by which was meant the later added 

 sandspit to the north. The argument was 

 then made that the ' mainland ' had once 

 extended some miles to the southeast, that 

 it had been worn away at first to a some- 



