424 TRANSACTIONS OF THE 



millions of francs, or nearly $700,000, have been annually ship- 

 ped from Alexandria. 



The exports of gums from Morocco reach from 200 to 300 tons, 

 and India from 1,500 to 1,600 tons. 



Gum arable of commerce is the produce of various species of 

 Acacia, particularly vera (true Acacia), a native of Arabia and 

 of Africa, from Senegal to Egypt, which supplies the finest qual- 

 ities. 



Gummifera (gum-bearing Acacia), a high thorny tree, found 

 near Mogador, the coast of Guinea, and in Ai"abia, form the Bar- 

 bary gum, a darker variety. The Senegal yields part of the Sen- 

 egal gum, the tears of which are usually in larger masses than 

 the Arabic, of a dark color, more clammy and tenacious. This 

 trade is chiefly in the hands of the French, from whom we occa- 

 sionally import it. In Cape Colony (Good Hope) gum is col- 

 lected by the Kaffirs from an acacia resembling the vera, which 

 Burchall calls capensis — probably it is the karoo of Hayne, Nies 

 and Ebermaier, which is abundant on the banks of the Orange 

 river, which reaches the Southern Atlantic Ocean, at about south 

 latitude, 29 degrees. It is of a pale yellow color and is not con- 

 sidered by the dealers so good as the gum of Northern Africa. 

 The ordinary Cape gum exudes spontaneously from the bark both 

 of the trunk and branches of the thorn tree (acacia horrida). 



A considerable trade was carried on a few years ago with Kaf- 

 firland, for the gum gathered from the mimosa tree. It was ex- 

 tensively used by calico printers, calenderers, makers of station- 

 ery, and in various industrial arts. The export has declined 

 from 4,876 cwt., in 1849, to 72 cwt. in 1853. The reason for 

 this decline is cimous. By mere accident it was discovered that 

 a gum could be manufactured from potatoes or wheat, wliich ar- 

 ticle, now called British gum (Dextrine), or gum substitute, has 

 superseded the more expensive in almost every department of 

 manufacture and art in which it was used. 



British gum is found to possess adhesive properties equal to 

 gum arable; being less liable to be affected by climate, it is 

 therefore used for postage stamps, envelopes, &c., as well as in 

 manufactures; and it can be produced for less than one-fourth 

 the cost. 



Some fortunes have been made by the discovery, which origin- 

 ated in pure accident. A fire took place in a manufactory of 

 starch from potatoes near Dublin. The burning building was 

 deluged with water from the fire engines, and the starch washed 



