INDEX. 279 



Gases: relation between the density of the gas and the quantity of 



heat extinguished or absorbed, i. 40 

 experiments on coloured gases, i. 40 

 table showing the absorption of various gases at a common pressure, 



or tension of one atmosphere, i. 41 

 table of absorption for one inch of tension, i. 4 

 causes of the difference between the absorptive power of compound 



and simple gases and vapours, i. 42 

 radiation equal to absorption, i. 46 

 action of different thicknesses of the same gas or vapour on radiant 



heat, i. 47 



dynamic absorption and radiation, i. 49 

 great opacity of a gas to radiations from the same gas, i. 52 

 the specific heat of compound gases generally greater than that of 



their component elements, i. 101 

 law of equivalency in weight of, i. 102 

 diffusion of, i. Ill 



Prof. Graham's experiments, i. 112 

 effusion of, 109, 110,113 



Prof. Graham's experiments, i. 113 



atmolysis, or method of analysing gases, i. Ill, 112, 114 

 internal movement of molecules of matter in a gaseous state, i. 113 

 coal gas, i. 1 17 



spectrum analysis of, i. 139 

 oxygen, i. 139 

 hydrogen, i. 139 

 nitrogen, i. 140 

 chlorine, i. 140 

 bromine, i. 140 

 iodine, i. 140 



superposed spectra of rarefied compound gases, i. 141 

 researches of M.M. Bunsen and Kirchhoff, i. 141 

 spectra of the rarefied vapours of: 

 sodium, i. 141 

 iron, i. 142 

 calcium, i. 142 

 strontium, i. 142 

 lithium, i. 142 

 barium, i. 142 

 magnesium, i. 142 



effect of high temperature on various spectra, i. 142, 143 

 effects of pressure on various spectra, i. 145 



