We shall be employed mainly with such algebraical func tions as are rational and integral. By a rational function of a quantity is meant one which contains that quantity in a rational form only; that is, a form free from fractional indices or radical signs. By an integral function of a quantity is meant one in which the quantity enters in an integral form only; that is, never in the denominator of a fraction. The following expres sion, for example, in which n is a positive integer, is a rational and integral algebraical function of x.