THE NATIONAL INSTITUTE. 
535 
1846 .] 
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 water, and is well 
worthy the attention of persons who traverse uncultivated countries, w T here they 
frequently suffer excessively from thirst, as in the traffic which is annually carried 
on between Independence, in Missouri, and Sante Fe, in Mexico, where it is ne¬ 
cessary to pass through regions but scantily supplied with water. 
There is a large tree growing very abundantly along the river at St. Augustin 
Bay, and also on the islands near Mozambique. The botanical relations of this 
tree I have not yet determined, not having been able to procure either flower 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 end, glau- 
cus beneath, dark green above, midrib distinct, 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 Guiacum officinale, this probably, also, may belong to 
the same natural family Tygophylleae. 
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 
caoutchouc. It is very abundant, and the gum appears to be used by the natives, 
but for what purpose, I could not ascertain. 
The mountains here furnish an abundance of lichen, the Rocella tinctoria, 
which 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 its large size, its paler color, and its broader 
flat fronds. 
It has been analyzed by Essenheck, who found it to contain a brown resin, wax, 
glutinous matter, chloride of sodium, tartrate and oxalate of lime. If digested in 
a weak solution of ammonia in a corked phial, at a heat not exceeding one hundred 
and thirty degrees, the plant yields a rich violet red color. Formerly litmus was pre¬ 
pared from this plant, but now it is obtained from the Leconora tartarea. At pre¬ 
sent the substance called orchil or archil, of which there is the blue and red, is the 
only coloring matter prepared from this lichen. Blue orchil is procured by steep¬ 
ing the lichen in an ammoniacal solution in a covered vessel. Red orchil is made 
with the same liquor in common earthen jars placed 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, is 
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 of Bourbon are at present engaged in the trade ; from 
that island it is exported to France. 
The natives here were using a kind of gum as food, 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 arabic, and the fracture is more conchoidal. 
The principal difference between this gum and gum arabic is, it contains more 
soluble gum and less water and ashes in analysis. The tree which yields this gum 
was not growing immediately on the 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 large 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 the Rhyzophorea ovata, and woven into a coarse cloth. 
The cattle are of the kind designated as the Bos Indicus, and are peculiar in 
having a large protuberance of fat immediately over their withers. 
The sheep are supposed to be aboriginal, and are covered with coarse hair, in¬ 
stead of wool. The ears are pendulous and the tails are very large, weighing 
from ten to twenty pounds, being composed of a mass of fat. 
