650 



REPORT OF NATIONAL MUSEUM, 1897. 



E. Characters depending upon the action of light: Light; transmis- 

 sion of light — diaphaneity; absorption of light — color, essential color, 

 nonessential color, and varieties of color; emission of light — phosphor- 

 escence; reflection of light — luster; refraction of light, uniaxial and 

 biaxial crystals; diftraction of light; polarization of light, by reflection 

 and simple refraction, double refraction, and absorption; interference 

 figures, isotropic class, anisotropic class; dispersion of the optic axes, 

 orthorhombic, monoclinic, and triclinic. 



F. Characters depending upon the action of the senses: Touch, 

 taste, and odor. 



G. Characters depending upon the resistance to chemical action: 

 Corrosion figures; solution planes. 



The visitor is advised to study the series in the order indicated by 

 the case lettering, regarding each panel as a unit, and reading from 

 left to right, beginning with the upper left-hand corner as in a book. 



I. CHEMICAL MINERALOGY. 

 THE ELEMENTS. 



The chemist has made known the existence of a number of kinds of 

 matter which can not be resolved into more simple forms. These kinds 

 of matter, of which there are about seventy at present known, are by 

 agreement called elements. The elements unite with and often replace 

 one another in certain constant proportions by weight. These weights 

 are expressed by numbers variously designated as equivalent, propor- 

 tional, reacting, and combining weights and as atomic weights. The 

 elements with their symbols and atomic weights are : 



Table of Atomic Weights. 



Name. 



Aluminum 



Antimony 



Argon 



Arsenic 



Barium 



Bismuth 



Boron 



Bromine 



Cadmium 



Calcium 



Carbon 



Cerium j Ce . . . 



Cesium ' Cs . . . 



Chlorine Gl . . . 



Symbol. 



Chromium .. 



Colialt 



Coluiiibium . 



Cojiper 



"Didymium ' 



Cr.... 

 Co.... 

 Cb.... 

 Cu.... 

 Di.... 



Atomic 

 weight. 



140.2 

 132. 89 

 35.45 

 52.14 

 58.93 

 94.0 

 63.60 

 142.00 j 



Name. 



Erbium 



Fluorine 



Gallium 



Germanium . 

 Glucinum . . . 



Gold 



Helium 



Hydrogen . . . 



Indium 



Iodine 



Iridium 



Iron 



Lanthanum . 



Lead 



Lithium 



Magnesium.. 

 Manganese. . 



Mercury 



Molj'bdenum 



Symbol 



Er. 

 F.. 

 Ga 

 Ge. 

 Gl. 

 Au 

 He. 

 H.. 

 In . 

 I .. 

 Ir . 

 Fe. 

 La. 

 Pb. 

 Li . 

 Mg 

 Mn 

 llg 

 Mo 



Atomic 

 weight. 



166.3 

 19.03 

 69.0 

 72.3 

 9.08 



197. 24 



1.08 



113.7 



126. 85 



193. 12 



56.02 



138. 06 



206. 92 



7.03 



24.29 



54. 99 



200. 



95. 98 



