Jantjaey 15, 1897.] 



SCIENCE. 



95 



the Dsemonelix ' regular ' of the topmost 

 beds. Though the development is too sud- 

 den and startling, nevertheless this is in 

 the order of occurrence. 



The paper was illustrated by a superb 

 and demonstrative series of lantern slides 

 and was listened to with the greatest in- 

 terest. The writer incidentally reviewed 

 the various, more or less absurd, explana- 

 tions of the ' Devil's corkscrews,' that had 

 been advanced, but in the end he estab- 

 lished his own views to the entire satis- 

 faction of those present. 



The Society at the conclusion of the paper 

 and after being joined by the other section 

 adjourned until the summer meeting. 



The separate section having in hand the 

 papers relating to petrography and crystal- 

 line rocks organized with Prof. Emerson as 

 Chairman and Mr. Turner as Secretary. 

 The first paper was the following : 



Notes on the Pre- Cambrian Volcanics of the 



South Mountain District. Florence Bas- 



COM, Bryn Mawr, Pa. 



By means of a map of the district and a 

 new and beautifully preserved series of 

 specimens, the textures of the old volcanic 

 rocks, such as spherulites, flow-lines, litho- 

 physse, etc., were illustrated. In certain 

 sections micropoikilitic textures were found 

 which are secondary as contrasted with the 

 views of Clements and Harker, who, in 

 other localities, regard them as primary. 

 Specimens of lithophyste were exhibited, 

 charged with piedmontite. 



Mr. Lane corroborated the interpretation 

 of the micropoikilitic texture as secondary 

 in many cases on Lake Superior and the 

 micropegmatitic as original. He empha- 

 sized the need of care in distinguishing 

 them. Mr. Iddings remarked that some 

 micropoikilitic textures were original and 

 some secondary beyond question, and Mr. 

 Cross, from his study of spherulites, corrob- 

 orated the same view. 



Notes on Roch Weathering. George P. Mer- 

 rill, Washington, D. C. 

 The paper began with a discussion of the 

 changes, both chemical and physical, which 

 have taken place during the decomposition 

 incidental to the reduction of a gray, mica- 

 ceous gneiss to the condition of a red, clayey 

 soil. The facts brought out by analysis 

 lead to a discussion of the possible forma- 

 tion of zeolitic minerals during the process 

 of decomposition and their efficacy as con- 

 servators of potash, as suggested by Lem- 

 berg and Hilgard. 



A series of analyses formed the basis of 

 the remarks and showed the great loss in 

 silica, alkalies and alkaline earths which 

 the process had caused, while the alumina 

 and iron oxides had largely remained. Alu- 

 mina was assumed as the constant mem- 

 ber and calculations were based on its per- 

 manence. The analyses, when recast on this 

 basis, furnished the ground for very inter- 

 esting deductions. The speaker had been 

 led by his investigations to question the ef- 

 ficacy of zeolites as conservators of alkalies. 

 A series of specimens in tubes were passed 

 around which had been obtained by wash- 

 ing a sample of a given weight and settling 

 it so as to separate the constituents accord- 

 ing to sizes. The chief red coloring ingre- 

 dient was found in the finest sediment of 

 all. The altered Medford diabase, as well 

 as the rock specially the subject of the pa- 

 per, were illustrated in this way. The 

 sorting had been done by Prof. Whitney, of 

 the Department of Agriculture. In discus- 

 sion J. F. Kemp remai-ked the permanence 

 of iron oxide in process of alteration, which 

 was surprising, as iron is a characteristic- 

 ally restless migrator, and also that phos- 

 phoric acid remained constant, whereas in 

 stock piles of Lake Superior hematite, it 

 may be largely leached from the upper por- 

 tions to the lower in a single season. L. 

 V. Pirsson emphasized the care that is 

 necessary in determining alumina and mag- 



