When the attention of inventors is directed to any one branch of mechanics, or to any one object, it is a matter of surprise how many improvements may be made on devices which seem at first sight near perfection. In no instance within our experience has this been more forcibly exemplified than in that of the velocipede excitement—almost a mania. No sooner does one of these improvements present itself than others follow, so that even the daily journals find it expedient to devote a department.of the paper to velocipede notes. One great objection urged against the bicycle is the difficulty of its management by beginners, and the degree of ex-pertness necessary to be attained to successfully nnage it. But it has its undeniable advantages. The bycicle, or two-wheeled velocipede, can turn corners that a tricycle cannot; it has less friction; is more under the control of the rider, and in all respects conforms more in its gyrations to his person than any three-wheeled concern could do; thus rendering him more independent of mere mechanical appliances. The poetry of motion —if there is such a thing—can be more easily shown by the course of the bicycle rider than by him who strides the three-wheeler, and thus the vanity of the expert is aroused, and he feels, like the skater, that the eyes of the world are upon him. It is, however, hard on beginners and the obese, those whose bodily activity has been for years directed to the brain. Imagine the hefty. editor of the SCIENTIFIC AMERICAN on a two-wheeler, with all his load of science and patents in his head; he would make a healthy show on a bicycle Here, however, in the accompanying engraving is just the thing—a three-wheeled or two-wheeled contrivance at the will of the rider. It is splendid. See the carelessness of the rider in the perspective engraving, then see the means by which he obtains his carelessness, shown in the accompanying diagrams. The axle carrying the rear wheels is Of a depressed V-form 165 (exaggerated in the diagrams to more forcibly present the idea). When the novitiate mounts the machine it is as represented in the Fig. 2, the wheels at the outer extremity of the crooked axle. Then it is an ordinary three-wheeled velocipede, la this state the rider may run for an indefinite distance; but when he has learned, he may, by a single movement of the lever seen in the perspective drawing, reverse the position of the axle by a half-revolution, and run the wheels together, as seen in Fig. 3. In this case the two wheels, where they impinge on the ground, are simply one. As these wheels are constructed to run on any portion of this crooked axle, no difficulty is experienced in holding them at any intermediate point desired, while they are prevented from coining together by a fixed collar, or flange, on the axle at the point where the two angles meet. In all other respects this velocipede is similar to others now in use. It is manufactured by Topliff & Ely, Blyria, Ohio. Patented February 23, 1869, through the Scientific American Patent Agency. Correspondence should be addressed as above.