PETROGRAPHY. 345 



Chklius, C. Die l;iini)r;)i>ljyii.scli('ii uiid jfiaiiiti>itr|»Iiyriscl)ftn Ganggesteine im 



Giuiulgebirgc ilea Spessarts iiiiil OdtMiwaldy. Nones .lalul). Min., Geol., etc., 



1888, II. Band, Erstes Hi ft, p. 07. 

 Clahkh, F. W., aud Merrill, Georgk P. On Nephrite and Jadeite. Proc. U. S. 



Nat. Mnsenm, 1888, p. 115. 

 CoHiON, E. Andalnsitfiiliicnde Granite. Nenes Jahrb. Min., Geol., etc., 1887, II. 



Band, p. 178. 

 Calls attention to the occurreuco of microscopic audalnsito in the granites of 



Klanse aud Kauhmiinzach in the Schwarzwald ; in Rochessou, Department of 



Vosges; Moszlaviua, Croatia ; and other localities. 

 Cole, Grenville A. J. The Rhyolites of Wnenheini, Vosges. Geol. Mag., July, 



1887, p. 299. 



On some additional occurrences of Tachylyte. Qnar. .Tour. Geol. Soc, No. 174, 



May, 1888, vol. xliv., p. :100. 



Describes the occurrence of tachylyte in Ardtnn, in Mull ; Kilmelfort, in Ar- 

 gyle ; Bryauslbrd, County Down, in Ireland ; aud among certain older rocks of 

 the Welsh border. One plate, with six; tigures, sliowiug micro-structures. 

 Collins, J. H. On the Geological History of the Cornish Serpentinous Rocks. Geol. 

 Mag., May, 1887, p. 220. 



Concludes that these are altered olivine, hornbleiule, or augite rocks. 

 Chrustchoff, K, von. Beweis fiirdeu urspriiuglich hyaliumagmatischan Zustand 

 gewisser echter Granite nnd grauitartiger Gesteiue. Neues Jahrb. Min., Geol., 

 etc., 1887, I. Band, zweites Heft, p. 208. 

 Crosby, W. O. Quartzites aud Siliceous concretions. Tech. Quarterly, May, 1888, 

 pp. 377-407. 



Discusses the origin of the secondary silica in quartzites and of the chalcedouic 

 nodules in calcareous rocks. 



Geology of the Outer Islands of Boston Harbor. Proc. Boston Soc. Nat. His- 

 tory, 1887, vol. XXIII, p. 450. 



Cross, Wiiit.man. Geology and Miniug Industry of Leadville, Colorado. Appendix 

 A. Petrography, Monograph xii, U. S. Geol. Survey, pp. :il9-:558. Two full-page 

 plates showing micro-structure. 



The rocks described are quartz-porphyries, diorites, porphyrites, rhyolites, 

 trachytes, and andesites. One of the more interesting rocks of the series is the 

 uevadite variety of the rhyolite. The sauidins of this rock often show a beauti- 

 ful satin-like luster, which is shown to be " due to the interfereuce of light iu 

 passing films of air between tlie extremely thin jjlates," info which the crystals 

 are divided by a series of partings parallel to the lustrous surface. Drusy cavi- 

 ties in the rock contain topaz iu very perfectly developed forms. The andesites 

 are in part hypersthenic, as previously described in Bull. No. 1, U. S. Geological 

 Survey. The quartz jiorphyries frequently carry the mineral allanite. 



Cross, Whitmax. Notes on the Henry Mountain Rocks. Geol. and Min. Industry 

 of Leadville, Colorado. Mono, xii, U. S. Geol. Survey, pp. 359-3G2. 



The rocks are hornblendic aud augitic porphyrites aud are briefly noted for 

 purposes of comparison with the rocks of the Leadville region. 



Notes on Phonolite from Colorado. Proc. Colo. Sci. Soc, 1887, pp. I(i7-174. 



This paper is of jtarficular interest as describing the second occurreuco of 

 phonolite yet known in the United States.* The rock has not as yet been found 

 iu situ., but in the form of bowlders of " local oiigin." and " apparently derived 

 from the hills to the southward," and on the eastern slope of the Hayilen 

 divide. 



* The only other known locality for this rock in the United States is the Black Hills 

 of Dakota, whore it was described by Caswell in 1880. 



