"Torch"

Earlier a special "torch" had been used to give a blind person an idea of the distance from, and the number and composition of objects around him. Curves could be detected and objects such as windows and curtains differentiated from chairs and tables in these experiments, he added.

Although the "torch" principle was enthusiastically received by American societies for the blind, it could not simulate the perception of the bat as the sounds had still to be interpreted and were very restricted in range and direction.