Carbonate of soda is obtained from the sal sola soda, extensively cultivated at Lanccrota and Forteventura.  It is gathered in September, dried, and then charred or fused into a ringing, hard, cellular mass, of a greyish blue colour.  A small quantity is made also at Grand Canary.  The barilla of the Canary Islands has been sold in England so high as 80l. a ton, and as low as 6l.; at the present time, (December, 1833) it is worth 9l. 10s. a ton.  The depreciation is caused chiefly by kelp, and other substitutes found in the British alkali, a French chemical discovery, manufactured from sea salt, from which, the other ingredients are detached, by combination with sulphur, and acids subjected to heat.  The imports of barilla from the Canary Islands to this country are about 3,500 tons a-year.  The United States of America, and of late years, Brazil, also, take off a few cargoes of this article.  Lancerota produces, annually, about 300 tons of barilla; Forte ventura about 1500 tons.

Rock moss (Parmelia perlata) is worth about 70l. a ton, and is one of the innumerable lichens common to the Canary Islands; it is used in the manufacture of cudbear for the dyers.  There is also a spurious kind, with difficulty distinguished from the good.

Silk is chiefly produced at Palma.  There is but little exported from Teneriffe.  It might, however, be produced in immense quantities, the white and red mulberry tree being indigenous and luxuriant in the middle region of the island, and the climate so mild, that the insect could be hatched and reared under wooden sheds, without any difficulty.  The great defect in the Teneriffe silk is the coarseness of the fibre, from want of dexterity in winding it off the cocoons, and in regulating the heat to which it ought to be subjected during that separation.

A considerable emigration used to take place annually from the islands, and particularly from Lancerota and Forteventura, to the Spanish Main, and to Cuba, where those islanders were much in request, as labourers and muleteers; and often prospered so well as to be enabled to return home enriched:  but the practice has been prohibited since the declaration of independence of Spanish South America.

There is a considerable fishery carried on from the Canary Islands, on the coast of Barbary, for a species of bream, which is salted in bulk, and sold very cheap, and in great quantities.  This trade is pursued in decked schooners, or lugger-rigged vessels, of from 60 to 70 tons burthen, which rum down before the trade wind to their station, where they remain until they procure a cargo, when they beat up to the island, take in a fresh cargo of Cadiz salt, and again return to their station.  They have very little intercourse with the Arab tribes of that coast, but they sometimes bring back a few lion, tiger, and leopard skins, and ostrich feathers.  I am happy to learn that our knowledge of the natural history of these islands is likely to be soon very much increased, by the indefatigable exertions of P.B.  Webb, Esq., a gentleman well known to the scientific world, who is now engaged at Paris in publishing the result of his researches in different branches of natural history.