Page:American Journal of Sociology Volume 3.djvu/609

Rh must be 1/16 of an inch from the vertical. The width of these strips added to the length of the back makes a total of 7½ inches; each strip is ½ inch wide; then the two make 1 inch; then 7½ inches, the combined length of sliding back and guides, from 8 inches in width between outside and outside of

short pieces, leave ½ inch; then, it there is a difference of ½ inch between actual width of hack and outside of frame, to make the back have equal distances on each end from outside of a frame; then we must divide ½ of an inch into two parts, which is ¼ of an inch; then the two half-inch strips are to be screwed on to the frame ¼ of an inch from the outside edge.

Tool performances aid and enforce recognition and appreciation of the mathematical. When we have repeated these operations through a series of models designed to meet the special mathematical defect, then we obtain mathematical quickening through tool performances.

In the upper left-hand corner is shown model No. 26 (p. 588), a scoop, as photographed, representing the actual model from