In acquiring a knowledge of numbers, as far as the senses are concerned, the eye and the touch are especially exercised; but it appears that the touch is the corrector of the sight: if fifty pieces of money be laid on a table, they will sooner and more accurately be numbered by the touch, than the eye; and we know in other instances, that the motion of the hand is quicker than the discernment of the sight. There are many circumstances, although they do not amount to a proof, which might induce us to consider, that the human hand has much contributed to our knowledge of numbers.[6] As far as we possess any direct evidence, none of the animals are capable of numerating; and this constitutes an essential difference between them and man in their intellectual capacities. In states of weakness of mind, this defect in the power of numerating, is very observable, and forms a just and admitted criterion of idiotcy; and it is well known that such persons exercise the organ of touch in a very limited degree, compared with those of vigorous capacity: their fingers are likewise more taper, and their sentient extremities less pulpy and expanded. The same state of the organ of touch may be remarked in some lunatics who have become idiotic, or where the hands have been confined for a considerable time. Although in our own language, we have not been able to discover any rational etymology of the units, that is, what was originally the meaning of one, two, three, &c., or of what these units were the representatives, we have, however, by the ingenuity of Mr. Tooke, a very probable account of the origin of ten, which means, that which includes, or comprehends all numeration; and that it does so include it, may be learned from the composition of eleven[7]; and if it should amount to no more than a curious coincidence, ten is the number of the manual extremities. Notwithstanding neither our own, nor any of the European tongues, afford us any probable solution of the actual meaning or import of the units, yet this contrivance is satisfactorily developed in the language of some of the African tribes, (vide Park's Travels, p. 337.) where it will be found, that when they had arrived at six, they proceeded by composition; not by the composition of six and one, to form seven, but by five and two. One--_Kidding_. Two--_Fidding_. Three--_Sarra_. Four--_Nani_. Five--_Soolo_. Six--_Seni_. Seven--_Soolo ma Fidding_--Five and Two. Eight--_Soolo ma Sarra_--Five and Three. Nine--_Soolo ma Nani_--Five and Four. Ten--_Nuff_.