(97) 



as well as the various qualities of paper into the structure 

 of which it enters. Here also are specimens of straw and 

 other specimens illustrating the several stages and sub- 

 stances connected with the production of straw paper. 



Rubber and Allied Products. Cases 37-39. — The first 

 case in the west wing contains rubber and allied pro- 

 ducts. Here are the implements and utensils used in 

 collecting the rubber "milk" from the trees which grow 

 in tropical forests. Rubber is derived mostly from trees 

 belonging to the mulberry family, spurge family, and dog- 

 bane family. Rubber, India-rubber, or elastic consists 

 chiefly of the peculiar substance caoutchouc, which, in the 

 form of an emulsion, constitutes the milky juices of many 

 plants, existing in special milk-tubes of the bark and wood. 

 The bark is cut or punctured, when the milk exudes and is 

 caught in some receptacle. The milk is coagulated by 

 various methods, mostly by subjecting it to the action of 

 smoke, and the coagulated mass, after losing water by 

 slow evaporation, takes on the dark color, toughness, and 

 elasticity characteristic of rubber. Rubber is more valu- 

 able in proportion as its percentage of caoutchouc is greater, 

 and that of its resin less. The most important source of 

 rubber is the tree Hevea brasiliensis, the Para Rubber tree, 

 native of Brazil, now very extensively planted in the East 

 Indies. 



Several varieties of rubber may be seen in the different 

 stages of refinement, together with some articles as manu- 

 factured for the market. Here, too, are two allied products, 

 gutta-percha and balata, which are derived from the 

 trunks and foliage of certain trees belonging to the sapo- 

 dilla family. These trees grow in many portions of the 

 tropics. 



Varnish Resins. Cases 40-42. — The varnish resins 

 proper are mostly dug from the earth, where they have 

 laid imbedded for ages in a sort of fossil state. Their 

 value for varnish purposes is due to the fact that they 

 dissolve with great difficulty, thus possessing the quality 



