Geology and Natural History. 179 



5. The Action of Radium, Roentgen Rays and Ultra- Violet 

 Light upon Minerals and Gems. — An article by G. F. Kunz and 

 C. F. Baskerville upon this subject is given in full in the issue 

 of Science for Dec. 18, 1903. A number of minerals, including 

 diamond, willemite, kunzite, pectolite, topaz, fluorite, autunite, 

 etc., were subjected to these different forms of radiation and a 

 considerable part found to respond. Of these, willemite, the 

 violet-colored spodumene called kunzite and diamond were the 

 most responsive to all forms of activity ; the possibility of the 

 presence of some undetermined element with the willemite (also 

 hydrozincite, etc.) is suggested. In the case of minerals from 

 Borax Lake, California, of different composition but which all 

 phosphoresced with ultra-violet light, though not with radium, 

 the existence of an element explaining this property is also sug- 

 gested. The whole subject is one calling for much additional 

 investigation. 



6. Optical Characters of Anthophyllite : a Correction ; by 

 C. H. Warren". (Communicated.) — The writer wishes to make 

 a correction regarding the optical orientation of the anthophyl- 

 lite from Rockport, Mass., described in this Journal, vol. xvi, 

 November, 1903, p. 341. The orientation should be: c' — c, 

 a = a, b = b, thus making the mineral optically negative. 



The error was due to the fact that a quartz wedge was used in 

 making the determinations, which was cut with the vibration 

 direction of fastest ray opposite to that of this ray in the wedges 

 to which the author had always been accustomed. Until very 

 recently no occasion had arisen to use this particular wedge for 

 the determination of a known mineral and so the error remained 

 unnoticed. 



7. Chemical Composition of Igneous Rocks expressed by 

 means of Diagrams ; by J. P. Iddings. U. S. Geol. Surv. Pro- 

 fessional Paper, No. 18, Washington, 1903, 4°, 92 pp., vm pi. — 

 The author of this paper was one of the first petrographers to 

 express the chemical relationships of igneous magmas, revealed 

 in their chemical analyses, by graphic means. In recent years we 

 have seen this instrument used by different petrographers in a 

 variety of ways to develop special features, but never before has 

 it been employed with so great a breadth of scope and on a plan 

 so comprehensive as in the present work. The idea is to express 

 pictorially to the eye the mutual chemical relations of all ana- 

 lyzed igneous rocks. For this purpose a double diagram method 

 is used. Each analysis has its molecular ratios calculated and 

 these are referred to a system of axes, and the points on the axes 

 connected with each other by lines. The triangles thus formed 

 are tinted with different colors and this enables the eye at a 

 glance to perceive the relations of the molecular oxides and their 

 capacity for forming feldspathic and ferromagnesian molecules. 

 These are the individual diagrams. The small individual dia- 

 grams so formed are then placed in a very large diagram in 

 which their centers or zero points are referred to a set of rec- 



