Raleigh, N. C, Nov. 8, 1852. Messrs. Editors—In No. 1, Vol. 8, of the Scientific American, I see it stated (as I have in previous numbers) that in America five horse-power, is allotted for driving a large rip saw, and a larger circular saw. In this statement there must certainly be some mistake, and such an one as will mislead many persons who are unacquainted with larger circular saws, and particularly in this " Piney Woods " country, in buying steam engines for driving circular saws. A circular saw of 52 inches diameter, and running 4,600 feet per minute at the teeth, cannot be driven in yellow pine timber (with the saw its full depth in the log) with less than 12 horse-power, and not less than a fifteen horse-power engine, should be employed to do the work ; I have built and put up in this State some of the best steam saw mills in the United States, and I find nothing less than 12 horse-power will give anything like satisfaction; 4,600 feet per minute is considered by our best sawyers, to be full fast enough (with a half inch teed to the revolution) to do good and profitable sawing. Henry G. Bruce. [When applied to about buying an engine for driving a large circular saw, we have always advised the purchase ot a ten horsepower engine. But a nominal five horse-power engine, has been asserted by what was considered good authority—a wholesale manufacturer of machinery—the requisite power. We are much obliged to Mr. Bruce for this definite and practical information—Ed.