Mr. Cooley, in his learned work, entitled "The Negroland of the Arabs[4]," seems to doubt if the Slave-Trade can be abolished or civilization advanced, in Central Africa, because of the neighbourhood of The Desert. This, however, is transferring the guilt of slavery and of voluntary barbarism, if barbarism can be crime, from the volition of responsible man to a great natural fact, or circumstance of creation--The Desert; and is a style of observation perfectly indefensible, as well as contrary to philosophy and facts. First, we cannot limit the stretch or progress of the Negro mind any more than that of the European intellect. Mr. Cooley himself admits that the Nigritian people have advanced in civilization. And if they have advanced, why not continue to advance? But so far contrary are facts to Mr. Cooley's theory, that The Desert, instead of being an obstacle to civilization, is favourable to it, whilst the Nigritian countries beyond the influence of The Desert are plunged into deeper barbarism. The reader will only have to compare my account of the Touaricks, with the recently published account of the social state of the kingdom of Dahomy, to convince himself how completely fallacious in application is Mr. Cooley's theory[5]. Slaves, too, abound in thickly populated countries as well as desert countries: witness China and India. The Sahara, also, has its paradisical spots, or oases of enjoyment, as well as its wastes and hardships. It is likewise, not true, that the Saharan tribes depend for their happiness on the possession of slaves, or that life in The Desert is galling and insupportable. Many a happy oasis is without a slave. However this may be, it is always an extremely dangerous line of argument, to represent moral depravity as springing necessarily from certain physical and unalterable circumstances of creation. Finally, to represent The Great Desert as the buttress of the Slave-Trade, is contrary to all our experience. In deserts and mountains we find always the free-men: in soft and luxurious countries we find the slaves. It is not the free-born Touarick who is the slave-dealer, or the stimulator of the slave-traffic, but the Moorish merchant, and the voluptuary on the coast who sends him. All that the Saharan tribes do, is to escort the merchants over The Desert; and they would still escort them over The Desert did they not deal in slaves, carrying on only legitimate commerce.