PHASES OF THE EARTHS DEVELOPMENT. 295 



SOME PHASES OF THE EAETH'S DEVELOPMENT IN THE 

 LIGHT OF RECENT CHEMICAL RESEARCH. 



By Professor EDWARD RENOUP, 



JOHNS HOPKINS UNIVERSITY. 



IN the following pages an effort is made to apply some of the results 

 of recent chemical research to the earlier- history of the earth. 

 It is hoped that the main facts brought out may be readily grasped by 

 those who have never studied chemistry, and that each link in the 

 chain of events will be made evident to those who have mastered the 

 rudiments of this science. 



Chemical action involves change of composition. Substances more 

 or less complex may be broken down into simpler substances, or from 

 several simpler substances a complex substance may be built up. From 

 the complex ore of copper found in nature the simple element copper 

 is obtained. From the elements sulphur and oxygen and the simple 

 substance water the complex sulphuric acid is built up. Within the last 

 few years the high temperature of the electric arc — the heat generated 

 by a powerful electric current playing between two carbon poles — 

 has been employed in bringing about chemical changes which do not 

 occur at ordinary temperatures nor at those obtainable by burning fuel. 

 The electric furnace is used industrially to make calcium carbide from 

 lime and coke, carbon silicide (carborundum) from coke and sand, and 

 the metal aluminum from its compounds. 



Chemical changes at high temperatures have long been an object of 

 research, but it was not until the introduction of the electric furnace 

 that it was possible to command temperatures high enough to make 

 exhaustive studies. In the last few years several chemists, especially 

 Moissan, of Paris, and his pupils, have done systematic work with the 

 aid of the arc furnace. The furnace used in the laboratory for high 

 temperature work is a small and simple apparatus; Moissan's furnace is 

 a block of quick lime a little longer and wider than a page of this 

 magazine and about three inches thick. A rectangular cavity is cut 

 on the upper surface of this block. A similar block forms the cover. 

 In opposite grooves between the top and bottom piece are placed the 

 carbons, such as are used in ordinary arc lights. The arc plays across 

 the cavity in such a manner that the substance to be heated is not 

 brought into the arc itself, which is vaporized carbon, but below it. 

 The cavity thus represents a tiny reverberatory furnace; the arc heats 

 the roof and sides to an intense heat, which is radiated on the open dish 



