four hundred miles of which is an uninhabited desert; yet caravans go regularly this immense distance.  The Russians and Chinese meet on the frontiers; where the furs, linen and woollen cloth, leather, glass, &c. of Russia, are exchanged for the tea, porcelain, cotton, rice, &c. of China.  This intercourse is very ancient.  There are also caravans of independent Tartars, which arrive on the Jaik and Oui, and bring Chinese and Indian commodities, which they interchange for those of Russia.

Tombuctoo is the great depot of central Africa:  with it the maritime states of Egypt, Tripoli, Algiers, Tunis, and Morocco carry on a very extensive and lucrative trade by means of caravans.  They take 129 days in travelling to Tombuctoo from the borders of the desert, but only fifty-four are spent in actual travelling.  There is also another caravan which sets off from Wedinou, and after collecting salt at West Tagossa, proceeds to Tombuctoo.  This goes as far as the White Mountains, near Cape Blanco, and is occupied five or six months in its journey.  The merchandize carried by these caravans is German linens, Irish linens, muslins, woollen cloth, coral beads, pearls, silk, coffee, tea, sugar, shawls, brass nails, &c. &c.  In exchange they bring back chiefly the produce of Soudan, viz. gold dust, gold rings, bars of gold, elephants’ teeth, gum, grains of paradise, and slaves.  There are also several caravans that trade between Cairo and the interior of Africa, which are solely employed in the traffic of slaves.  There can be no doubt that caravans arrive at Tombuctoo from parts of Africa very distant from it, and not only inaccessible, but totally unknown, even by report, to Europeans, and even to the inhabitants of North Africa.

What a picture does modern commerce present of the boundless desires of man, and of the advancement he makes in intellect, knowledge, and power, when stimulated by these desires!  Things familiar to use cease to attract our surprise and investigation; otherwise we should be struck with the fact, that the lowest and poorest peasant’s breakfast-table is supplied from countries lying in the remotest parts of the world, of which Greece and Rome, in the plenitude of their power and knowledge, were totally ignorant.  But the benefits which mankind derives from commerce are not confined to the acquisition of a greater share and variety of the comforts, luxuries, or even the necessaries of life.  Commerce has repaid the benefits it has received from geography:  it has opened new sources of industry; of this the cotton manufactures of Britain are a signal illustration and proof:—­it has contributed to preserve the health of the human race, by the introduction of the most valuable drugs employed in medicine.  It has removed ignorance and national prejudices, and tended most materially to the diffusion of political and religious knowledge.  The natural philosopher knows, that whatever affects, in the smallest degree, the remotest body in the universe,