68 o POPULAR SCIENCE MONTHLY. 



grown to be a city of a hundred thousand inhabitants, with mod- 

 ern features, and Manaos, up the river, is fast following it. India 

 rubber is the mainstay of the northern Brazilian states, Bolivia, 

 and eastern Peru. Brazil has a great advantage in its immense 

 waterway ; ocean-going steamers run twelve hundred miles up 

 the Amazon, whereas every African river except the Congo has a 

 bar at its mouth and cataracts not far distant from the coast line. 

 It is, besides ivory, about the only commodity produced in the 

 interior of a tropical country that will bear the expense of trans- 

 portation, often on the heads of natives along tangled man-paths, 

 to the seaboard. So in many places it has been the basis of first 

 commerce. The principal trees in South America are the Mani- 

 liot Glaziovii, the Ficus gameleira, and varieties of the Castilloa, 

 the Hevea, and the Hancoriiia. " The production of Par?i rubber,'^ 

 says the Scientific American, December 5, 189G, "increased from 

 8,243,000 pounds in 1865, to 15,144,000 in 1875, 29,310,000 in 1885, 

 and 46,363,000 pounds in 1895; the great advance in the decade 

 between 1885 and 1895 being the direct result of the increased 

 demand produced by the tire-makers. Last year 37,456,000 pounds 

 were delivered to manufacturers in the United States, against 

 31,062,000 pounds in 1894 and 35,583,000 pounds in 1893. The 

 highest price paid in this country last year for fine Para rubber 

 was eighty-one cents and a half in November." The United States 

 has been from the first the largest consumer, and an American 

 syndicate, it is said, is now seeking capital to develop ten million 

 acres in the Orinoco Valley, chiefly with a view to profits from 

 the great virgin rubber forests known to exist there. 



Enormous supplies are stored up in Africa and her adjacent 

 islands, where a variety of Ficus and great climbing shrubs, the 

 Landolphia and Valiea, produce it. Stanley alludes to great 

 numbers of these climbers entwining the trees, so as to make 

 passage exceedingly troublesome. Attempts to force the price to 

 unreasonable limits are therefore not likely to meet with perma- 

 nent success, and we may banish fears of approaching exhaustion. 

 The gum fully thrives, seemingly, nowhere but in the tropics. 

 " It is the one jungle product which society finds indispensable," 

 said The Spectator recently, and, further : " Everybody knows that 

 in the last five years the use of pneumatic tires for cycles and 

 solid rubber tires for horse- vehicles has enormously increased our 

 consumption of this article ; but, quite apart from that more obvi- 

 ous fact, India rubber is daily being introduced more and more 

 into all sorts of machinery. Highly competent judges say that 

 if the output could be doubled within a year, so many applica- 

 tions would instantly arise that the price would not fall appre- 

 ciably." The negroes have no regard for the climbers, and cut 

 them down in order to extract the utmost possible amount of sap. 



