How to Make a Hygrometer

Mount a wire on a board which is used for a base and should be 3/8 by 4 by 8 in., as shown in the sketch.
A piece of catgut—a string used on a violin will do—is suspended from the bent end of the wire.
A hand or pointer is cut from a piece of tin and secured to the catgut string about 1/2 in. from the base.
A small piece of wood and some glue will fasten the pointer to the string. The scale is marked on a piece of cardboard, which is fastened to the base and protected with a piece of glass.

How to Make a Hygrometer
Simple Hygrometer

—Contributed by J. Thos. Rhamstine.
Excerpt from the book:
THE BOY MECHANIC
VOLUME I
700 THINGS FOR BOYS TO DO
WITH 800 ILLUSTRATIONS
1913, BY H. H. WINDSOR CHICAGO
POPULAR MECHANICS CO. PUBLISHERS