[Illustration: FIG. 2.--SILHOUETTE PORTRAITS.]
_Silhouette Portraits_.--Take a large sheet of paper, black on one side and white on the other, and affix it to the wall, white surface outward, by means of pins or tacks. Place a very bright light upon the table, at a proper distance, and allow the person whose portrait it is desired to form to stand between it and the wall (Fig. 2). Then, with a pencil, draw the outlines of the shadow projected. While this is being done, it is very necessary that the subject shall keep perfectly immovable. When the outlines are sketched, remove the paper from the wall and cut out the portrait. After this, all that remains to be done is to turn the portrait over and paste it to a sheet of white paper. The silhouette is profiled in black, and if the operation be skillfully performed, the resemblance will be perfect.--_La Nature_.
Our readers have often seen grocers' clerks or employes of business houses break the string with which they had tied up a package, by seizing it with the hands, bringing the latter close together, and then suddenly separating them with a quick movement. If it be thought that this quick motion is sufficient, let any one try it, and he will merely cut his hands without breaking the string, provided the latter has some little strength. In order to succeed, the cord must be arranged in a certain manner, as we shall explain.
[Illustration: MODE OF BREAKING A CORD WITH THE HANDS.]
The cord to be broken is placed upon the left hand, and one of its ends is passed over the other in such a way as to form a cross, and the end forming the shorter part of the cross is wound around the fingers (it should be left long enough to make several turns). The other end is then turned back and wound around the right hand, so as to leave a space of about eighteen inches between the latter and the left hand. If these directions are properly followed, the string should have the form of a Y in the middle of the hand, as shown in the lower figure of the accompanying engraving.
It is only necessary after this to close the hand, after seeing that the Y is very taut, and to seize the cord with the other hand, as shown in the upper figure. This done, the two hands are brought together and then suddenly separated so as to give a quick pull on the point of junction of the Y-shaped branches, which form a true knife. It will be readily seen that as the cord is broken suddenly the shock does not have time to transmit itself to the hands. This is an interesting demonstration of the principle of inertia.