152 FIRST YEAR COURSE IN GENERAL SCIENCE 



Sulphur, under ordinary conditions, is a lemon-yello\v 

 crystalline solid. It has been obtained for centuries from 

 fissures in the rocks of volcanic regions. Sicily has exported 

 great quantities to the United States and to other countries, . 

 Extensive subterranean beds of pure sulphur have recently 

 been discovered in Louisiana, and the United States is now 

 exporting more sulphur than it imports. 



Sulphur is burned in rooms which are infected by certain 

 contagious diseases, because the sulphur oxide formed by its 

 combustion destroys disease germs. This oxide is irritating 

 if breathed in small quantities, and when breathed in large 

 quantities, it is fatal. 



166. Properties of Metals. There are certain physical 

 properties which belong especially to metals : 



Luster, shining surface. 



Malleability, capability of being hammered or rolled into 

 thin sheets without breaking. 



Ductility, capability of being drawn into wire. 



Conductivity, ability to transmit heat and electricity. 



Fusibility, capability of being melted. 



No two metals possess all these properties in the same de- 

 gree; and the characteristic properties of each metal vary 

 greatly, because of the effect of temperature and other con- 

 ditions. Each of the metals has its own peculiar combina- 

 tion of properties by means of which it can be identified. 

 Each metal has its own specific gravity, its own peculiar 

 color, its own degree of tenacity and of elasticity, and 

 other special properties. 



167. Iron. At the present day, iron in its various forms 

 is the most important of the metals. Its properties make it 

 the best metal for car rails, steamships, locomotives, frames 

 of buildings, and machines, all of which are necessary to the 

 life of our times. 



Wrought iron is the most nearly pure of the commercial 

 forms of iron. Steel contains a small per cent of carbon; 



