This Simple Device Is Useful in Enlarging or Reducing Drawings and Maps
Assuming that a contour map is to be enlarged, the rectangular divisions of the original map, ordinarily section lines or the boundaries of quarter sections, are drawn on the larger sheet as a base for the reproduction. Place the device on the original map, as indicated, the edge of the rubber band touching a “horizontal” section line between two “vertical” ones, the rubber band under slight tension. On the black surface of the band, dot white points, with water color, along the section line at which the contour lines intersect it. Also place a dot at each end of the band to indicate the position of the two “vertical” section lines between which the band is set.
Transfer the device to the same relative position on the enlargement, stretching the rubber band. Make dots at each end, denoting the “vertical” section lines, for the corresponding lines on the enlargement. The series of intermediate points along the band will be in the same relative position on the enlargement as they were on the original. They can be connected on the enlargement with as accurate a result as obtained by the use of proportional dividers, and more rapidly.
After the points are indicated upon the enlargement, the reproducing device is removed and the surface of the rubber band cleaned instantly by touching it with a moist cloth. The exposed part of the rubber band is a variable, and the device can be made with this dimension adapted to the work. It is capable of enlarging or reducing at a ratio not greater than six to one, above which the rubber band approaches its elastic limit.—H. L. Wiley, Seattle, Wash.
Signal Telegraph with Green and Red Lights
By arranging a circuit with batteries, lights, and keys, as shown in the diagram, a signal telegraph may be made that will afford much pleasure to boys and may be used for practical purposes. The keys A and B are wired into the circuit with a battery C and a red and a green incandescent lamp. A simple set of signals may be devised easily so that messages may be sent in the code.—James R. Townsend, Itasca, Texas.
A Circular Swing
By DAVIS FOSS GETCHELL
While on the farm I constructed a circular swing which proved very attractive to my boys and their friends. By its side, and suspended from the same tree branch, was an ordinary swing. During the eight weeks of our stay the latter was seldom in use. The circular swing was a far greater favorite with all the young people, boys and girls alike.