154 



SCIENCE, 



[Vol. IV., No. 81. 



become as good a scientific thinker as Faraday 

 or Darwin ; but to-day, while fallacies of the 

 crudest kind are rampant in every field of dis- 

 cussion, from religion and party-politics to 



biology and political economy, something less 

 ethereal and impalpable than this statement of 

 the necessity of philosophic doubt would have 

 been far more useful. 



RECENT PROCEEDINGS OF SCIENTIFIC SOCIETIES. 



Academy of natural sciences, Philadelphia. 



July 8. — Professor Angelo Heilprin described a 

 new trilobite from Walpack Ridge, about ten miles 

 north of the Delaware Water-Gap. The tail-piece, 

 which was the only part of the animal found, indi- 

 cated an individual some six or seven inches or more 

 in length, and clearly demonstrated its relationship 

 to the genus Phacops, sub-geftus Dalmania. Among 

 its faunal associates were Phacops Logani, P. (Dal- 

 mania) pleuroptyx, Acidaspis tubercularus, Spirifer 

 macropleura, Atrypa reticularis, Strophomena punc- 

 tulifera, S. rhomboidalis, Orthis subcarinata (or O. 

 multistriata ?), Merista sp., etc. The horizon is that 

 known as the Stormville shales (lower Helderberg), 

 evidently the equivalent of the Delthyris shales of 

 the New- York geologists. 



Philosophical society, Washington. 



April 26. — Prof. J. R. Eastman reported the dis- 

 covery of a mass of meteoric iron at Grand Rapids, 

 Mich. An analysis by Dr. F. W. Taylor gave : iron, 

 94.54; nickel, 3.81; cobalt, 2.40; insoluble, about .10; 



total, 100.85; specific gravity, 7.53. Mr. William 



H. Dall read a paper entitled 'Certain appendages of 

 the Mollusca.' Mr. J. S. Diller read a communi- 

 cation on the volcanic sand which fell at Unalashka, 

 Oct. 20, 1883, and some considerations concerning its 

 composition. The substance of this communication 

 has already appeared in Science. There ensued a 

 general discussion of the nature and properties of 

 volcanic dust, and of the theory which ascribes recent 

 peculiar meteorologic phenomena to the dust ejected 

 from Krakatoa. Capt. C. E. Dutton argued that the 

 formation of volcanic dust particles by the bursting 

 of bubbles tends to give them a somewhat definite 

 general size, and does not produce a large amount of 

 dust fine enough for indefinite suspension. The op- 

 posite view was maintained by Prof. H. M. Paul, and 

 was sustained by Mr. Diller, who said that the micro- 

 scope revealed no limit to the fineness of the Kraka- 

 toan dust. The higher the magnifying-power applied, 

 the greater the number of particles visible ; and this 

 relation extends to the limits afforded by the capacity 

 of the instrument. Professor Paul thought the vio- 

 lence of the Krakatoan explosion was competent to 

 charge the atmosphere at very great altitudes, and 

 considered the fineness of the dust a sufficient expla- 

 nation of its indefinite suspension. Mr. William B. 

 Taylor suggested that electricity might be an efficient 

 cause of suspension. It is a common phenomenon 

 of volcanic eruption ; and dust particles charged with 

 the same kind of electricity as the earth would be 



repelled not only by one another, but by the earth. 

 The period elapsing between sunset and the red after- 

 glow testifies to the great altitude of the phenome- 

 non; and at such altitude the air is not only very 

 rare, but is anhydrous, and the discharge of electri- 

 city is impossible. 



May 10. — Mr. G. H. Williams of Johns Hopkins 

 university addressed the society on the methods of 

 modern petrography, classifying them as chemical, 

 mechanical, optical, and thermal, and explaining 

 their several functions. There followed a sympo- 

 sium on the question, 'What is a glacier?' Mr. I. C. 

 Russell defined a glacier as an ice-body originating 

 from the consolidation of snow in regions where the 

 secular accumulation exceeds the loss by melting and 

 evaporation (that is, above the snow-line), and flow- 

 ing to regions where loss exceeds supply (that is, be- 

 low the snow-line). Mr. S. F. Emmons denned it as a 

 river of ice, possessed, like an aqueous river, of move- 

 ment and of plasticity. In virtue of plasticity, it 

 adapts itself to the form of its bed. The neve field is 

 the reservoir from which it derives its supply of ice, 

 and the initial impulse of movement. Until the neve 

 moves from its wide and shallow bed into a narrower 

 and deeper one, and thus gives outward proof of the 

 plasticity of the ice of which it is composed, it does 

 not become a glacier. It may become crevassed, and 

 it may carry blocks of rock on its surface without 

 losing its neve character. Mr. W. J. McGee said that 

 the phenomena of glacier ice and neve belong to a 

 graduating series, and can be only arbitrarily discrimi- 

 nated. He regarded as artificial and incompetent, 

 classifications depending on acclivity of the ice-bed, 

 on constriction of the ice-body, on ability to sustain 

 bowlders, and on rate of motion. All things consid- 

 ered, the most satisfactory line of demarkation is the 

 snow-line. Mr. William H. Dall discriminated masses 

 of ice moving in a definite direction from fields of ice 

 practically stationary, restricting the term 'glacier' to 

 the former. A glacier is a mass of ice with definite 

 lateral limits, with motion in a definite direction, and 

 originating from the compacting of snow by pressure. 

 Prof. T. C. Chamberlin said that the subject illus- 

 trated the fact that hard and fast lines belong only 

 to nomenclature, whereas nature is characterized by 

 gradations. The true distinction in this case is not 

 structural, but genetic. There is an area of growth 

 and an area of waste to every glacier. It is only 

 superficially that the area of growth coincides with 

 the neve, and the neve field is accurately defined only 

 on the summer day of maximum waste. Capt. C. E. 

 Dutton said that his intended remarks had been an- 

 ticipated by Professor Chamberlin. Definition can 



