662 PROCEEDINGS OF THE BALTIMORE MEETING 



"In this definition there are three points : first, that the pyroxene component is last 

 consolidated ; second, that it occurs in areas which are larded, as meat is larded for 

 cooking, with streaks of older crystals ; and thirdly, that these crystals are much flat- 

 tened or elongated. Velain, for example, in his Conferences de Petrographie (page 59), 

 speaks of the ophitic texture as characterized by the elongation of the feldspathic ele- 

 ment, and its distribution through the areas of the ferruginous element (pyroxene). But 

 it has often happened that only the first or third point has been taken to be essential to 

 the definition. Lapparent (Geologie, 1883, page 630) alludes to the tendency of the 

 feldspar to form elongate crystals as characteristic of the ophites, but his figures and 

 descriptions show the areas of pyroxene in which they are embedded. We find that in 

 their experiments on the reproduction of rocks, Fouque" and Levy apply the term ophite, 

 not to all rocks having elongate feldspar or xenomorphic pyroxene, but to those only that 

 have the structure above described." 



Present Usage 



Inasmuch as prominent petrographers are therefore not in accord as to the 

 meaning of the word, it is desirable to determine, if possible, what meaning was 

 given to it by its author, and what modifications of that meaning, if any, are 

 justified, either by the usage of the author of the term or by any other means. 

 At the same time its relation to other terms of similar meaning may be advan- 

 tageously brought to light. 



The word has been used in its narrow sense by Lane,* Harker, 5 Wadsworth, 8 

 Judd, 7 Rutley, 8 and Teall. 9 



Rosenbusch, 10 in 1887, made it a synonym of his diabasic (diabasische-kornig) 

 structure in some statements, but in others he uses it in the narrower sense. In 

 1901 he used ophitic as synonymous with doloritic, diabasic, and divergent- 

 strahlig. If less pyroxene and some residual glass were present he called the 

 structure intersertal. Kemp 11 used ophitic in the wider sense in the first edi- 

 tion of his well known "Handbook of Rocks," but in later editions he changed 

 to the narrower meaning. Lacroix 12 defined the term in the narrow sense in 

 1896, but in 1899 he used it in the wider sense. Among others who have used 

 the word in the broader sense are Zirkel, 1 * Williams, 14 Loewinson-Lessing, 18 

 Rinne, 16 Lawson," Clements. 18 



Original Definition 

 As mentioned by Michel Levy in the definition quoted by Lane, the former 



* Loc. clt. See also Bulletin of the Geological Society of America, vol. 18, 1906, p. 648. 



5 Petrology for students, 1897, p. 126. 



6 Geological and Natural History Survey of Minnesota, Bulletin 2, 1887, p. 107. 



7 Quarterly Journal of the Geological Society, 1885, p. 360 ; 1886, p. 68. 



8 Granites and Greenstones, 1894, p. 14. 



9 British Petrography, 1888, p. 135. 



10 Mikr. Phys., 2 auflage, 1887, II, pp. 190, 191. Elem. Gest., 2 auflage, 1901, p. 326. 



11 Handbook of rocks, 2d ed., 1900, pp. 44, 158 ; 3d ed., 1906; pp. 71, 210. 

 13 Min^r. France, II, 1896, p. 34. Le Gabbro du Pallet, 1899, p. 28. 



13 Lehrb. Petr., 1893, I, p. 689. 



14 U. S. Geological Survey, Bulletin 62, 1890, p. 196. American Journal of Science, 

 vol. xliv, 1892, pp. 482, 492. 



15 Geological Survey of Michigan, vol. vi, part 1, p. 227, footnote. 

 18 Gesteinskunde, 1901, p. 87. 



17 Geological Survey of Canada, Annual Report, vol. iii, 1887, p. 58F. 

 i 8 U. S, Geological Survey, Monograph xxxvi, 1899, p. 200. 



