SCIENCE. 



609 



are pierced with holes which represent the stems ot up- 

 1 ight plants, thickets of which were buried by the descend- 

 ing showers or rapidly accumulating sediment of volcanic 

 ash. Here the source of the materials is to be sought in 

 the line of great volcanic vents which crown the summit 

 of the Cascade Mountains, and from which, at intervals, 

 were emitted either floods of lava, poured down on to 

 the plain along the eastern border of the range, or 

 showers of ashes which, borne inland by the prevailing 

 westtrly winds, fell on forest, savannah and lake, tem- 

 porarily destroying animal and vegetable life and form- 

 ing, when falling or washed into water basins, stiata 

 which alternate with fossil beds, the accumulations of 

 quieter times. In other places these tufaceous deposits 

 were washed from all the highlands into the valleys, 

 forming local masses of considerable ihickness without 

 the intercalated beds mentioned above. 



The accompanying section, copied from my report on 

 the Geology of Northern California and Oregon (Pacific 

 R. R. Report, Vol VI, Geology, p. 47), will illustrate the 

 deposition of these tufaceous rocks in the lake basins 

 where they are inters' ratified with the fossiliferous beds. 



THE SCIENTIFIC SOCIETIES OF WASHING- 

 TON, D. C. 



The Philosophical Society.— During the month 

 of November three very important papers were read : 

 cn the Anomalies of Sound Signals, by President James 

 C. Welling ; on the Storage of Electric Energy, bv Mr. 

 J C. Koyl ; and on Baiometric Hypsometry, by Mr. G. 

 K. Gilbert. 



The first named paper was a comprehensive review of 

 the vexed discussion concerning the anomalies observed 

 in the transmission of sound, and the summation of the 

 result in a series of twelve aphorisms. The second paper 

 was by a fellow of Johns Hopkins College, with reference 

 to a series of experiments lately made by him in company 

 with some Washington gentlemen upon an invention for 

 the storage of electricity. Mr. Gilbert's communication 

 had reference to a scheme of measuring altitudes by 

 means of two barometric stations in the same vicinity, 

 the one quite elevated, the other as low as convenient. 

 By this means the influence of the thousand and one local 

 causes affecting the barometer would be more thoroughly 

 brought under the knowledge of the observer. 



The Biological Society. — The following com- 

 munications have been made during the past month : on 

 the Philosophy of the Retardation of Development 

 Among the Lower Animals, by Prof. C. V. Riley ; An- 

 tiquity of Certain Types of North American Non-Marine 

 Mollusca, and the Extinction of Others, by Dr. C. A. 

 White ; Recent Explorations of the U. S. Fish Com- 

 mission, by Mr. Richard Rathbun. 



Professor Riley drew the attention of the society to a 

 number of instances where the development of insects 

 had been retarded in the embryo stage for a very long 

 time. This did not refer to the well known retardations 

 of whole broods, but to wholly exceptional cases. The 

 speaker altributed the phenomena to evolutionary causes, 

 and showed how a species might be saved from the 

 wholesale destruction of a very severe winter or other 

 disaster by this means. 



Professor White's paper had reference to the survival 

 from very high antiquity of many of the fresh water and 

 brackish water forms, and to the total disappearance of 

 others, for which events no adequate causes can be as- 

 signed. 



Mr. Rathbun 's communication was a review of the 

 work of the Fish Commission from its foundation, illus- 

 trated by a map locating every dredging station ; by a 

 papier mache model of the Atlantic bottom as tar out as 

 the deep soundings, from the mouth of the St. Lawrence 

 southward, and by specimens of the apparatus employed 



as well as Ihe fauna discovered. The address was neces- 

 sarily very comprehensive, but exceedingly interesting. 

 At the same time the attention of the society was called 

 to a pamphlet by Prcf. G. Brown Gcode, entitled " The 

 First Decade of the United States Fish Commission, its 

 Plan of Work and Accomplished Results, Scientific and 

 Economical, Salem, Mass.: Salem Press, 1881." 



The Anthropological Society.— Three papers 

 were also read before this society in November, to wit : 

 How Shall the Deaf be Educated ? by President E. M. 

 Gallaudet ; a Navajo Myth, by Mr. R. L. Packard ; the 

 Regulative System of »he Zunis. by Prof. J. Howard 

 Gore. The educaiion of the deaf must be preceded by a 

 proper classification of the heterogeneous group com- 

 monly called deaf mutes. The question of the relative 

 superiority of the sign language and of visible speech 

 was discussed with great minuteness. The author also 

 treated the problem of heredity, of relative intelligence, 

 and of the power of abstraction, with great ability. 



Mr. Packard's myth was one taken by him last summer 

 from one of the Navajo tribe and related to the origin of 

 the Navajos. 



Mr. Gore has spent some years upon the evolution of 

 deliberative assemblies and the conduct of such bodies. 

 Last summer, being in charge of a surveying party in 

 New Mexico for the government, he availed himself of 

 his opportunities to become familiar with the customs of 

 the Pueblo Indians in such matters. These papers will 

 be published in the proceedings of the Society. 



DIAGRAMMATIC REPRESENTATION OF STE- 

 ' REOSCOPIC PHENOMENA. 



(Continued from p. 548, Nov . 1881, in Transactions 0/ N. Y. 



Academy of Sciences). 



In a previous article ( s ) it has been shown that no reliance 

 can be placed upon the theory of apparent distance in 

 the stereoscope, elaborated by Wheatstone and Brewster, 

 and applied in the diagrammatic explanation of stereo- 

 scopic phenomena in all our text books on Physics. We 

 may well ask, therefore, to what extent it is possible, by 

 any diagram, to represent the position of objects as. they 

 should appear in the stereoscopic field of view. So far 

 as this is determined by the relation between the visual 

 lines we may secure an approximation only by the follow- 

 ing method, in which it must be assumed that we know 

 also the relation between the camera axes at the time the 

 photograph was taken. Since the visual lines may be 

 practically regarded as special secondary axes to the crys- 

 talline lenses, it will be found convenient to call them 

 visual axes, and their possible relations, axial convergence, 

 parallelism, and divergence. It may be well also to re- 

 state two principles thai have been sufficiently demon- 

 strated elsewhere. 



I. A point farther or nearer than the point of sight is 

 necessarily seen double ( 9 ) and with imperfect focaliza- 

 tion. If farther, the internal rectus muscles of the eye- 

 balls must be slightly relaxed to make it the point of 

 sight; if nearer, they must be contracted. Such relaxa- 

 tion is habitually associated with remoteness, such con- 

 traction with nearness, of the point fixed. 



II. If an external poinl: is imaged upon corresponding 

 retinal points, the subjective effect is that of union of the 

 two eyes into a central binocular eye, the nodal point of 

 which is the point of origin in all estimates of direction 

 and distance. ( I0 ) 



A brief preliminary proof of a geometrical principle 

 to be applied is also necessary. Let C and C, fig. i, be 

 two fixed points, and E midpoint between them on a 

 horizontal plane. Let this plane be cut by four vertical 

 planes, parallel to each other, their traces being marked 

 I, II, III, and IV. Let Band Q beany points of plane I, 

 from which straight lines are drawn to E, piercing plane 

 II at A and P respectively. Through C and C let pro- 



