xx CONTENTS. 



Change in oilier elementary bodies. Verification of these results with 

 the chlor-hydrogen photometer Page 271 



MEMOIR XX. 



ON THE ALLOTROPISM OF CHLORINE AS CONNECTED WITH THE 

 THEORY OF SUBSTITUTIONS. 



Chlorine exists in two states, active and passive. Decomposition of water 

 by it in the sunlight. Facts connected with this decomposition. The 

 relations of chlorine and hydrogen. The allotropism of chlorine. 

 Connection of these facts with the theory of substitutions 284 



MEMOIR XXL 



ON THE INFLUENCE OF LIGHT UPON CHLORINE, AND SOME REMARKS 



ON ALCHEMY. 



Modification of chlorine by the sun-rays. The modification is not tran- 

 sient. Alchemical attempts to modify metals. Exposure of silver 

 chloride to a burning-lens. The resulting silver is not acted upon by 

 nitric acid 312 



MEMOIR XXII. 



ON THE ACTION OF GLASS AND QUARTZ ON THE RADIATIONS THAT 

 PRODUCE PHOSPHORESCENCE. 



Phosphorescence by rays from a Leyden spark through quartz. From 

 the voltaic arc. It is occasioned by the more refrangible rays. Im- 

 perviousness of glass. Professor Henry's experiments. Comparison 

 of the chemical and phosphorogenic rays 316 



MEMOIR XXIII. 



ON A REMARKABLE DIFFERENCE BETWEEN THE RAYS OF INCANDES- 

 CENT LIME AND THOSE EMITTED BY AN ELECTRIC SPARK. 



Non-permeability of glass to spark radiations. Permeability to calcium- 

 light radiations. Different refrangibility of the spark and the cal- 

 cium-light radiations. Shadows imbedded in Canton's phosphorus. 

 Evolution of old shadows in an order of succession 320 



MEMOIR XXIY. 



ON THE ELECTRO-MOTIVE POWER OF HEAT. 



Experimental arrangement to determine the electro-motive power. Tem- 

 peratures calculated from quantities of electricity. Increase of tension 



