1846.] THE NATIONAL INSTITUTE. 535 



had been a spring there some time before, and that the soil was still damp. The 

 natural vegetation is thus frequently a certain indication of \vat<ir, and is well 

 worthy the attention of persons who traverse uncultivat- d counliies, where they 

 frequently suffer excessively from thirst, as in the traffic whicii is annually carried 

 on between Independence, in Misstiuri, and Santo Fe, in Mexico, wht)reit is ne- 

 cessary to pass through regions but scantily supplied with water. 



There is a largo tree growing very abuhdantly along ihe river at St. A^'gustin 

 Bay, and also on ihe islands near Mozambique. The botanical relations of this 

 tree I have not yet determined, not having been able to procure either flowt-r or 

 fruit. It is a large tree, the trunk generally inclined, with a smooth, slightly ru- 

 gose bark. The leaves are opposite, slender-ovate, tapering to each enii, ghiu- 

 cus beneath, dark green above, midrib distmct, petiole short. The wood is heavy, 

 difficult to split, and the fibres cross each other in a very regular diagonal man- 

 ner. 



As no other tree is known to botanists in which the fibres of the wood are disposed 

 in this manner, except the Guirtcum officinale, this probably, also, may bulung to 

 the same natural family Tygoph3'lleae. 



Should this wood prove valuable in cabinet work, any demand might almost be 

 supplied here. 



On the long extent of shingle which stretches south of the river is found a tree 

 which belongs to the genus Euphorbia, which furnishes a notable quantity of 

 cnoutchouc. It is very abundant, and the gum appears to be used by the natives, 

 but for what purpose, 1 could not ascertain. 



The mountains here furnish an abundance of lichen, the Rocella tinctoria, 

 whicli is also largely obtained at the Canaries, Azores, and on the western coast of 

 Africa, together with another species, the fuciformis. In 1840, four thousand one 

 hundred and seventy-five hundred weight of this moss was imported into England. 

 The latter species is sometimes called in commerce "Madeira-weed." It is dis- 

 tinguished from the Rocella tinctoria by itslarge size, its paler color, and its broader 

 flat fronds. 



It has been analyzed by Essenbeck, who found it to contain a brown resin, wax, 

 glutinous matter, chloride of sodiii ii, tartrate and oxalate of lime. If digested in 

 a weak solution of ammonia in a corked phinl, at a heal not exceeding one hundred 

 and thirty degrees, the plantyields a rich viol't red color. Formerly litmus was pre- 

 pared from t'.iis plant, but now it is obtained from the Leconora tartarea. At pre- 

 sent the substance called orchil or archil, of which there is llie blue and red, is the 

 only coloring matter prcpiired from this lichen. Blue orchil is procured by steep, 

 ing the lichen in an ammoniacal solution iu a covered vesspl. Red orcliil is made 

 with the same liquor in common earthen jars pluced in a room heated by steam. 

 It is employed for coloring, dyeing, and staining. 



The excessive aridity of these mountains during a great part of the year, ia 

 highly favorable to the growth of this lichen, as it is never developed in damp 

 places, groves, or situations deprived of intense light and heat. 



The French of the island ol' Bourbon are at present engaged in the trade ; from 

 that island it is exported to France. 



The natives here were using ii kind of gum as fiod, which in appearance and 

 form seems identical with gum Senegal. It is of a reddish color, in large tears, 

 more difficult to break than gum arable, and the fracture is more conchoidal. 

 The principal difference between this gum and guin arable is, it contains more 

 soluble gum and less water and ashes in analysis. The tree which yields this gum 

 was not growing immediately on tho coast, and I was therefore unable to ascertain 

 what tree produced it. From the manner in which it was used, I presume it is 

 abundant. 



The articles cultivated here by the natives consist principally of rice, corn, 

 pumpkins, sweet-potatoes, a largo bean similar to the lima, and a small quantity 

 of cotton of an inferior quality, which is spun into yarn by the females, dyed with 

 the bark of llio Rhyzophorea ovata, and woven into a coarse cloth. 



The cattle are of the kind designated as the Bos Indicus, and are peculiar iu 

 having a large protuberance of fat immediately over their withers. 



The sheep are supposed to bo aboriginal, and are covered with coarse hair, in- 

 stead of wool, Tho ears are pendulous and tho tails are very largo, weighing 

 from ten to twenty pounds, being composed of u mass of fat. 



