448 THE UNIVERSE. 



When speaking of vegetable secretions, we cannot, in 

 the present day, omit a beantiful tree of the family of 

 Sapotacete, formerly considered nseless, but which fur- 

 nishes us with one of the most precious substances- 

 gutta-percha. Spread over the coasts of Sumatra and 

 Java, its produce has only been advantageously worked 

 during the last twenty years. Like the gold of CaUfornia, 

 this tree has caused great social changes in the countries 

 where it grows. 



In Caracas, in South America, grows the cow-tree, 

 which, when its trunk is wounded, furnishes an abundant 

 supply of milk, of which the traveller can confidently drink 

 freely, for it unites all the qualities of the milk of our 

 domestic animal, which it entirely replaces in some coun- 

 tries of America. 



One of the trees which yield our internal economy ser- 

 vices as important as the preceding is the butter-tree. It 

 furnishes the negroes of the Niger Avith a secretion which 

 they substitute for the ingredient used in our kitchens, and 

 with Avhich they prepare all their food. It is sold abun- 

 dantly in their markets, where it is known as shea-butter.^ 



be certain that this phenomenon was not due to any aberration of vision, he as- 

 sociated to himself another observer, who was to indicate by a signal the moment at 

 which he perceived the luminous spai'ks. The learned Swede became convinced that 

 there could be no illusion, for his companion saw the lights at precisely the same 

 instant that he did. — Haggren, Memoire sur les Fleiirs qui donnent des Eclairs. 

 Tradnit du Suedois dans le Journal de Pliysique, t. xxxiii. p. 111. These passing 

 gleams are sometimes seen iu quick succession, but they often only appear at 

 intervals of several minutes. They are best seen on flowers of an orange yellow ; 

 the pale varieties of the same species do not produce them. They may be ob- 

 served in the marigold, the monkshood, the tagetes [Tagetes erecta, Linn.), and 

 the heliotrope. 



' The shea butter-tree {Fentadesma huti/racea), which thrives vigorously by the 

 Ijanks of the Niger and iu all the central and western zone of Africa, seems des- 

 tined some day to effect a great social revolution in the districts where it grows. 

 Karl MuUer says that the slave merchants consider it far more formidable than 

 the blockade kept up by the English. As the natives collect more butter than 



