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SCIENCE 



[Vol. IY., No. 



least abundant. He moreover observed the constant 

 tendency on the part of pyroxene to be arranged in 

 layers alternating with either calcite or apatite, as 

 well as abundant evidence that pyroxene passed by 

 hydration into serpentine, a process which could be 

 seen in every stage at any of the localities visited. 

 From these data it was assumed that siliceous waters, 

 permeating limestones originally evenly dolomitic, 

 would cause the local development of pyroxene by 

 the change of the magnesium carbonate into the cor- 

 responding silicate. Were it the case, as so often 

 occurs, that this pyroxene was developed in layers, 

 its subsequent alteration to serpentine or loganite 

 would readily account for all the appearances' exhib- 

 ited by the eozoon, without the necessity of appeal- 

 ing to organic agencies. 



The Tuesday afternoon session of the section'was 

 almost exclusively devoted to geographical papers 

 and discussions. These had hitherto scarcely re- 

 ceived their due share of attention; but now proved, 

 owing to the presence of several distinguished mem- 

 bers of the British association, of unusual interest. 

 Sir James Douglass was called to the chair, while 

 Capt. Bedford Pirn, P.N., presented a paper on the 

 geographical and commercial advantages of the Nic- 

 aragua route across Central America. Capt. Pirn is 

 especially fitted to speak upon this subject, on ac- 

 count of long experience and the much careful study 

 which he has devoted to the different plans which 

 have been proposed for inter-oceanic communication. 

 He exhibited a section surveyed under his direction, 

 between the years 1863 and 1867, across Nicaragua, 

 and explained how a canal could be constructed at 

 comparatively small expense, for the transference of 

 ships raised upon pontoons drawing only from four 

 to eight feet of water. The principal objection to 

 Mr. de Lesseps's canal across Panama was not, he 

 thought, the practical difficulties of construction, — 

 although these were very great, — but the almost con- 

 stant, and long-continued calms prevailing on the 

 Bay of Panama. He himself had once been becalmed 

 there for eleven months. This paper elicited numer- 

 ous questions and remarks from various members of 

 the section, among them a somewhat extended com- 

 munication by Kear-admiral Ammen, who had served 

 as a member of the commission appointed by the 

 U.S. government to inquire into the relative merits 

 of the various routes proposed for securing a passage 

 for ships across Central America. 



Mr. Ashburner, of the second geological survey of 

 Pennsylvania, then proceeded to give a brief account 

 of the work accomplished during the past ten years, 

 the period of the survey's existence, as well as of its 

 future aims and plans. He was succeeded by Mr. 

 Trelawney Saunders of London, who has been so 

 active in prosecuting the recent survey of Palestine 

 under the auspices of the Palestine exploration fund. 

 His first paper contained an account of a remarkable 

 journey over an entirely unknown portion of Tibet, 

 Mongolia, and the frontiers of India and China, by 

 Kreshna, a native surveyor trained under the trigo- 

 nometrical survey of India. This was only accom- 

 plished after four years of unparalleled hardship, but 



has made most important additions to the geograph- 

 ical knowledge of Asia. Mr. Saunders's second paper 

 related to the geography of Palestine, in connection 

 with which the great map of the survey was exhibited. 

 Several exceedingly interesting points were explained, 

 where the geographical researches had succeeded in 

 definitely locating sites of biblical events, as well as 

 shed much light upon many heretofore doubtful and 

 difficult allusions in the sacred writings. 



The proceedings of Wednesday were introduced by 

 an extended biographical notice of the late Professor 

 Arnold Guyot, by his assistant, Mr. William Libbey, 

 jun., of Princeton. Mr. Libbey's paper will appear 

 in full in the Journal of the American geographical 

 society of New York. Mr. William M. Davis of 

 Cambridge gave some valuable hints as to geo-j 

 graphic classification, based upon the study of plains, 

 plateaus, and their derivatives. He traced the his- 

 tory of an area undergoing gradual elevation through 

 a regular course of development, likening it to the 

 successive phases in the life of an organism. His 

 remarks, which laid special stress upon the educa- 

 tional value of such studies, were admirably illus- 

 trated by a series of paper models showing different 

 stages of development in the history of a plateau. 



Professor H. Carvill Lewis of Philadelphia de- 

 scribed a narrow trap dyke, which he had succeeded 

 in tracing continuously across south-eastern Penn- 

 sylvania for upwards of ninety miles through Bucks, 

 Montgomery, Delaware, and Chester counties. The 

 dyke, which is generally only visible as a line of 

 bowlders, has been apparently faulted in several 

 places; one great fault of several thousand feet up- 

 throw being coincident with a large lateral displace- 

 ment of both trap and the adjoining strata. Another 

 important fault in the triassic formation was also 

 mentioned, whereby the entire thickness of this for- 

 mation is exhibited. The trap dyke is distinct lith- 

 ologically from other dykes, and does not mark a 

 fault, although passing through the Laurentian, 

 Cambrian and Triassic formations. 



Professor Persifor Fraser, from a study of a point 

 in the archean-paleozoic contact-line in south-eastern 

 Pennsylvania near Gulf Mills, concluded that the 

 hydro-mica schists which outcrop there were older 

 than the accompanying limestones, and hence not 

 to be considered as metamorphosed Silurian strata. 

 Professor Carvill Lewis could not agree with these 

 conclusions regarding the structure of this locality; 

 although Professor James Geikie of Scotland, who had 

 recently visited the spot in company with Professor 

 Fraser, expressed himself as entirely convinced of 

 the correctness of the latter' s views. 



Papers relating to glacial phenomena, which had 

 been so abundant at the Minneapolis meeting, were 

 but scantily represented in Philadelphia. Mr. J. C. 

 Smock spoke of the remains of local glaciers recently 

 examined by him in the Catskill Mountains; and 

 Prof. J. C. Chamberlain, in presenting a paper by 

 Mr. J. E. Todd, exhibited upon a large map the 

 course of the moraines along the upper Missouri 

 Kiver, and explained the effects which these had pro- 

 duced upon the drainage of the region. 



