Water Mills. - Although we are, in this country, provided with many contrivances, in which the united powers of water, steam, and mechanical force, have been successfully applied to the purpose of grinding corn into flour, yet we have not, till very lately, met with floating water mills, to be worked by tides, or currents ; and which are farther designed to put in motion, machinery adapted to any kind of manufacture. - Messrs. Polfreeman, of Long-acre, in conjunction with Messrs. Allen, Fos-senden, and Gray, have purchased the patent-right of Mr. Hawkins ; and have lately completed one of those mills; which, by permission of the Board of Navigation, is stationed between London and Blackfriars Bridge. Such grant was obtained with the laudable view of reducing, if possible, the price of flour in the metropolis, and furnishing a constant supply of that necessary article of subsistence. - The simplicity of this invention renders a long description superfluous ; as it consists in merely applying the force of two or three water-wheels on each side of a barge, or any other vessel better calculated to contain the interior part of the machinery. Thus, we venture to pronounce, that the advantages to be derived from this contrivance, must be almost incalculable, both to the metropolis and the kingdom in general (see Bread, vol. i. p. 333) 3 for, independently of the great expence of steam-engines, there will necessarily result from it, an annual saving of several thousand chaldrons of coal.