4QO SCIENCE PROGRESS. 



Lang, Heinr. Otto. Das Mengenverhaltniss von Calcium, 

 Natrium und Kalium als Vergleichpunkt und Ordnungs- 

 mittel der Eruptivgesteine. Bull. Soc. Beige. Geo/., vol. v., 

 pp. 123-146 (and French abstract, pp. 192-196), 1891. 



Lang, Heinr. Otto. Versuch einer Ordnung der Eruptiv- 

 gesteine nach ihrem chemischen Bestande. Tsch. min. it. petr. 

 Mitth. (N.S.), vol. xii., pp. 199-252, 1891. 



Lang, Heinr. Otto. Beit rage zur Systematik der Eruptiv- 

 gesteine. Ibid., vol. xiii , pp. 115-169, 1892. An essay 

 towards a purely chemical system, based on the relative pro- 

 portions of Ca, Na, and K in the bulk-analysis. 



(31) ADAMS, FRANK D. Notes to Accompany a Tabulation of 



the Igneous Rocks based on the System of Professor H. 



Rosenbusch. Canad. Ree. Set., pp. 463-469, 1891, with 

 table. 



(32) ROSENBUSCH, H. Ueber Structure und Classification der 



Eruptivgesteine. Tsch. min. u. petr. Mitth. (N.S.), vol. xii., 

 PP- 351-396, 1891. 

 {ll) IDDINGS, Joseph Paxson. The Origin of Igneous Rocks. 

 Bull. Phil. Soc. Washington, vol. xii., pp. 89-214, 1892. [The 

 special feature of Iddings' work is a graphical method of 

 comparing rocks by means of diagrams expressing the varia- 

 tions of their bulk-composition.; 



(34) Zirkel, Ferdinand. Lehrbuch der Petrographie. second 



edition, 3 vols. 8vo. Leipzig, 1893-4. [With a discussion 

 of the principles of classification, vol. i., pp. 829-842. The 

 prime division adopted is that between the even-grained 

 rocks (chiefly plutonic), and the porphyritic and glassy 

 (chiefly volcanic), the latter being divided into pre-Tertiary 

 and Tertiary (with post-Tertiary). The mineralogical 

 divisions are based in the first place on the predominance 

 of alkali-felspars or lime-soda-felspars or the absence of any 

 true felspar, and secondly upon quartz and the ferro- 

 magnesian minerals.] 



(35) BROGGER, W 7 . C. Die Eruptivgesteine des Kristianiagebietes. 



I. Die Gesteine der Grorudit-Tinguait-Serie. Vidensk. 

 Skr. {Math, naturv. Klasse), No. 4, 1894. 



(36) ROSENBUSCH, H. Mikroskopische Physiographic der Massigen 



Gesteine, third edition, enlarged and revised. 8vo. Stuggart, 

 1895. [First part only. The author, while admitting the 

 essential identity of the older and younger volcanic rocks, 

 still retains the distinction.] 



Alfred Harker. 



