We witnessed a few days since the operation of the improved printing press for printing on both sides of a sheet of paper at once, patented by M. S. Beach, of the New York Sun, about a year since, and notwithstanding the imperfect and hurried manner in which the parts were put together for the trial, the impressions obtained were of such a perfect character as to warrant us in declaring the invention a complete success, and a valuable improvement on Hoe's " last fast." The improvements are simple, and easily understood. They consist in arranging on the type drum, where the balance weight ordinarily occurs, a second form, so that after the sheet is printed on one side, as heretofore, it can be brought back by an extremely ingenious contrivance, and printed on the other side from this second form, thus successively printing on both sides of the sheet without in any manner interfering with the usual motion of the press, and performing double the amount of work. In reality the adaptation of this improvement to the press enables an increased number of sheets to be printed beyond that produced by its double impression character. In other words, the same speed of type and cylinder surface which produces 20,000 impressions on Hoe's ten cylinder press, gives 44,000 impressions per hour on this one. There is another improved feature in the printing " register " of this press of Mr. Beach's, which for simplicity, ingenuity, and effectiveness, recommends itself to all engaged in " the art preservative of all arts." We congratulate the ingenious inventor of this simple and thoroughly effective press on the accomplishment of an object upon which he has expended so much time, labor, skill, and expense, and pursued with such untiring energy for a series of years past.