This investigation was supported, in part, by Research Grant No. RD-2557-S-68-C1 from the Social and Rehabilitation Service, U.S. Department of Health, Education, and Welfare.
2.
WiedelJ.W., and GrovesP.A.“Tactual Mapping: Problems of Design and Interpretation,”International Journal for the Education of the Blind, 18: 10–16, (1968).
3.
All illustrations have been redrafted from tactual form to visual form for reproduction in this article.
