270 degrees; Fahrenheit, becomes pliable, 

 soft and tough : or, if the amount of sulphur 

 be increased, of a horny consistency and com- 

 pressible with great difficulty. 



Until it has been Vulcanized, rubber is so 

 sensitive to heat and cold as to be practically 

 valueless in summer heat it becomes soft and 

 sticky; while winter's cold renders it brittle and 

 unelastic. 



RUBBER 



WHAT IT IS AND HOW IT GROWS 



This little book has been prepared especially for 

 Schools, and is now used by Teachers in all parts of 

 the country. It will be furnished free to Teachers 

 making application. 



Soconusco Development Co. 



RUSS BUILDING 

 SAN FRANCISCO, CALIFORNIA 



Soconusco Development Company's Rubber 

 Plantation, LosTocAYOS, adjoins La Zacualpa, and 

 is under the same management. 



44 



