62 



SCIENCE. 



[N. S. Vol. I. No. 3. 



intrusive or dike type and the effusive type 

 was pointed out. The main object of pre- 

 sentiug the paper at this time is to elicit the 

 best methods of measuring the coarseness of 

 grain of a rock, the object being to express 

 by some arithmetical or mathematical form- 

 ula based on statistics, or in some other def- 

 inite way, the relation of texture to walls 

 and thickness in a dike. The paper elicited 

 considerable discussion by Messrs. Hovey, 

 Kemp, Iddings, Cross, and G. P. Merrill, in 

 which the following points were made ; the 

 large size of the phenocrysts in some very 

 narrow dikes ; the importance of not meas- 

 uring minerals of the intratellurio stage ; 

 the great variability of circumstances under 

 which dikes cooled, as heated or cold walls, 

 pressure, mineraUzers, etc., and the difficult- 

 ies of getting rehable data of the kind re- 

 quired by Dr. Lane. 



19. Crystallized Slags from Copper smelting. 

 Alfred C. Lane, Houghton, Michigan. 

 This paper described (with exhibition of 



specimens) slags from the cupola furnaces 

 used in coppersmelting, which contained 

 large mehUte crystals, between one and two 

 centimeters square, interesting optically and 

 in mode of occurrence. Crystallized hema- 

 tite was also noted. 



The specimens elicited great interest on 

 account of the size and perfection of the 

 crystals. 



20. On the Nomenclature of the fine-grained 

 Siliceous Bocks. L. S. Geiswold, Cam- 

 bridge, Mass. 



The writer described the difficulties met 

 first, in his study of novaculite, and later, 

 in connection -with other siliceous rocks, 

 such as cherts, jaspers, etc., in applying defi- 

 nite names. The troublesome characters of 

 opaline, chalcedonic and quartzose silica, as 

 regards the origin of each, presented obsta- 

 cles both for mineralogic and genetic classi- 

 fication. 



This paper elicited an interesting dis- 

 cussion which threatened at times to take 



up the whole subiect of the classification of 

 rocks. The general feeling seemed to be 

 that rocks could best be named primarily 

 on a mineralogic and textural basis, and 

 that these priucii^les furnished the best so- 

 lution of the difficulties presented by the 

 paper. The speakers were Messrs. Wolff, 

 Emerson and Lane. 



21. 0)1 Some Dykes containing ' Huronile.^ 

 By Alfred E. Barlow, Ottawa. (Eead 

 by F. D. Adams.) 



This paper contained a brief petrographi- 

 cal notice of certain dykes of diabase con- 

 taining ' Huronite,' as the mineral was 

 originallj^ named by Dr. Thomson, of Glas- 

 gow, in Ms Mineralogy of 1836. Dr. B. J. 

 Harrington's re-examination of this mineral 

 in 1886 showed some very gi-ave errors in 

 Thomson's work and the ' huronite ' must 

 simply be regarded as an impure or altered 

 form of anorthite, which has undergone 

 either pai-tial or complete ' saussuritiza- 

 tion,' owing to metamorphic action. Cer- 

 tain localities were mentioned north and 

 northeast of Lake Huron, where these dykes 

 have been noted cutting the Huronian as 

 well as the granitoid gneisses usuall_y classed 

 as Laurentian. Mr. A. P. Low, of the Can- 

 adian Geological Survej^, noticed dykes con- 

 taining this mineral cutting the Laurentian 

 and Cambrian in the Labrador Peninsula. 



22. The Granites of Pike''s Peak, Colorado. 

 Edward B. Mathews, Baltimore, Marj^- 

 land. (Introduced by W. B. Clark.) 

 This paper gave an area! and petrographi- 



cal description of the granites composing 

 the southern end of the Rampart or Colo- 

 rado range and showed that great macro- 

 scopic variation may result, while the micro- 

 scopic characters remain monotonously uni- 

 form. Four types in all were distinguished, 

 based on the size of phenocrysts and coarse- 

 ness of gi-ain. The paper was discussed by 

 Whitman Cross and J. P. Iddings, after 

 which the section adjourned to meet again 

 at 4:30 p. m. 



