-c^®© 



I 



FIR-TREE GUMS. BITUMEN. 



41 



PINE AND OTHER FI R-TRE E GUM S . — TUR P E NT IN E, &c 



The abundance and commonness of these substances in 

 northern climates render it quite unnecessary to treat of their 

 production and native qualities. The importance of their use, 

 particularly that of pitch and resin, in combination with caout- 

 chouc, when submitted to the process of vulcanization, is only 

 now beginning to be known. 



They have, together with coal-tar, asphaltum, &c., in some 

 cases been used in small quantities by both American and 

 English manufacturers of gum-elastic. The sudden temporary 

 advance of caoutchouc to a very high price, in 1851, has in- 

 duced the writer, as well as the manufacturers of caoutchouc, 

 to attempt their use with that of coal-tar in larger quantity ; 

 and it has been found that some of them, if not all, when prop- 

 erly treated, may be used with great advantage in some of the 

 vulcanized compounds in equal proportions with caoutchouc. 



BITUMEN OF VARIOUS KI NDS . — AS PH ALTUM, 

 COAL-TAR, &c. 



Considering the vegetable origin of these substances, it would 

 be reasonable to suppose they would be found to combine read- 

 ily with caoutchouc, and also be susceptible of vulcanization 

 when combined with it. This has proved to be the fact with 

 regard to them. They are also found valuable, not only on 

 account of their abundance and cheapness, but also because 

 they serve to give a polish or lustre to the articles when it is 

 desired, and likewise to prevent the effervescence of an excess 

 of sulphur in the fabrics. 



