FIG. 1.—AN AQUATIC VELOCIPEDE OF 1822.
The amusing engraving of this velocipede, which is mentioned under the name of the aquatic tripod, puts us in mind of another document of the same kind that we have seen in the gallery of prints of the National Library. It is a naively drawn lithograph representing a trial of velocipedes in the Luxembourg Garden, at Paris, in 1818. In Fig. 2 we give a reduced copy of it. It will be seen that in 1818 velocipedes were made of wood and were provided with two wheels—one in front, and the other behind. The propelling was done by alternately placing the feet on the ground.
FIG. 2.—A TRIAL OF VELOCIPEDES IN 1818.
A SUNSHINE RECORDER.
The apparatus is of simple construction. It consists of a glass sphere silvered inside and placed before the lens of a camera, the axis of the instrument being placed parallel to the polar axis of the earth. The whole arrangement will be readily understood by an inspection of Fig. 1. The light from the sun is reflected from the globe, and some of it, passing through the lens, forms an image on a piece of prepared paper within the camera. In consequence of the rotation of the earth, the image describes an arc of a circle on the paper, and when the sun is obscured, this arc is necessarily discontinuous. The image is not a point, but a line, and in certain relative positions of the sphere, lens, and paper, the line is radial and very thin, so that the obscuration of the sun for only one minute is indicated by a weakening of the image.
