Hand Talk, or Plains Sign Talk, is a trade language that was once the lingua franca across what is now central Canada, the central and western United States and northern Mexico, used among the various Plains Nations.
"Sign language is so faithful to nature and so natural in its expression that it is not probable that it will ever die. It has a practical utility, and should not be looked upon merely as a repetition of motions to be memorized from a limited list, but as a cultivated art, founded upon principles which can be readily applied by travelers. Sign language may be used to advantage at a distance, which the eye can reach but not the ear, and still more frequently when silence or secrecy is desired." William Tomkins