Messrs. Editors.—In the 25th number of the present volume you correct an error of one figure in Vol. 6, page 272, Sei. Am., I entirely agree with Mr. Sloan, that "the articles on water wheels in Vol. 6 are valuable, and that any error however small, should be carefully corrected." I would direct your attention to some other slight errors in those articles. In the preceding number, page 264, Vol. 6, the following extract of the specification of a patent issued the 10th of July, 1847, to the undersigned, appears, viz. :—" I make the area of the cross section of the shute (or of all the shutes) by which the water is let on the wheel, equal to that of all the issues at which it leaves it. To produce a maximum effect the shutes and issues of the wheel, should be of equal size, and they move with the same velocity as the water." There is an error in the last sentence—"and they," should read. " and the wheel." There are some errors on page 408, of the same volume. In the second paragraph— article " Hydraulics "—the word " volition," should have been " rotation," and the third paragraph—a description of figure 67—is misplaced. It should have been inserted attei the first sentence ot the fifth paragraph, aftei the words,'o in diagram, figure 67." As it is it is thrown in between the announcement oi a principle and its illustration. As you advocate the claims of persons whe first publish to the world a discovery, I hop" you will indulge me in a few remarks on the above principle of having the area of a crosi section of the inlet, equal to that of the issue; of the wheel. This principle of action of water on a turbine [by the term " turbine," from the Latin " turben," a whirling, a whirlwind, a vortex I presume, I understand, wheels that receivi the water with a whirling, motion,] watei ! wheel, I claim to have discovered by th investigation of the principles of hydrodyna mics, and not by experiments, experiments, however, have since verified the result. This principle I published to the world, in 1847, by having it recorded in the Patent Office, and then again in 1851, in the Scientific American. But why at this late date should it be attempted to fix the discovery on Mr. Parker ? Mr. Parker claims the discovery of giving the inlet water a whirling motion, and so far as my information extends, he is entitled to it, in this country at least. But in France, perhaps, h was preceded by Fourneyron, who commenced the investigation in 1823. But that he discovered or practiced prior to 1847, the principle of making the inlet and outlet of equal sectional area I deny. In a description of Parker's wheel in the Journal of the Franklin Institute, nothing of the kind is mentioned, but, on the contrary, the inlet is said to be variable, and no mention made of the reduction ot the co-efficient of effect thereby. In the article referred to (page 272, Vol. 6, Scientific American.) it is stated that the inlet was 10J inches, and the issues of the wheel 9 inches ; but by making the correction it leaves the issues 6 inches, or something more than one half that of the inlet, which agress with the practice of his agents at the South. And I have not seen any publication that intimated that they should be of equal size, until the one in question of the 5th of March, 1853. J. B. CONGER. Jackson, Tenn.