Such being the evidence in favour of the hypothesis respecting the Congo, the objections against this theory must be admitted to be weighty and formidable. The principal of these are, 1. That it supposes the course of the Niger to lie through the vast chain of the _Kong_ Mountains (anciently _Montes Lunæ_), the great central belt of Africa. Of the existence of these mountains there appears to be no doubt; and from their situation in the midst of a great continent, they may reasonably be supposed to be of vast size and extent; in which case it is difficult to understand, how the Niger could penetrate this barrier, and force a passage southwards. 2. The course of the Niger, estimated from its source in the mountains of Senegal (supposing it to be the same river with the Congo, and to flow by Wangara and Cashna through the centre of Africa into the Atlantic), would be considerably more than 4000 miles. But the course of the Amazon, the greatest river in the old or new world with which we are acquainted, is only about 3500 miles; and, although the existence of a river considerably greater than any yet known, may be within the limits of physical possibility; yet, so improbable a supposition ought not to be adopted upon slight or conjectural reasoning, or upon any thing much short of distinct and positive proof. To give such a vast extension to the Congo upon the grounds stated by Mr. Maxwell, might justly be considered as one of those exaggerations, to which, according to a remark of D'Anville, geographical writers upon Africa have always been remarkably prone, 'en abusant, pour ainsi dire, du vaste carrière que l'intérieur de l'Afrique y laissoit prendre.' (Mém. de l'Academie des Inscriptions, Tom. xxvi p. 61.) [Footnote: The following scale (taken from Major Rennell's Memoir of a Map of Hindostan, p. 337,) shewing the _proportional length_ of some of the most considerable rivers already known, may be useful to the reader on the present occasion. EUROPE. Thames 1 Rhine 5-1/4 Danube 7 Wolga 9-1/2 ASIA. Indus 6-3/4 Euphrates 8-1/2 Ganges 9-1/2 Burrampooter 9-1/2 Ava 9-1/2 Jennisca 10 ASIA CONTINUED. Oby 10-1/2 Amoor 11 Lena 11-1/2 Hoanho (China) 13-1/2 Kian Keu 15-1/2 AFRICA. Nile l2-1/2 AMERICA. Mississipi 8 Amazon 15-3/4 It must be observed, however, that the _magnitude_ of a river depends much less upon the length of its course than upon the number of auxiliary streams which fall into it. It is this latter circumstance, which occasions the vast size of the Ganges, compared, for example, with the Nile; although the course of the latter is so much longer. Rivers not fed by auxiliary streams, may even become _smaller_ in consequence of the length of their course. The editor is indebted for these observations to Major Rennell.]