So it turns out that jungle gyms, patented in 1920 by an Illinois lawyer, were intended to help children understand Euclidean 3-space in the hope this would make it easier to eventually understand 4-space! Who knew? According to another site: << Math on the Playground ---------------------- [Sebastian] Hinton had in mind a game for children on the jungle gym. The jungle gym was a three-dimensional space. Hinton's game made physical the Cartesian coordinates that name points in space on three axes, x, y, and z. When [an ordered triple of numbers] was called out, the children would climb on the bars to find the named location. Seems like an odd game for a lawyer to invent, doesn't it? Not if you consider Hinton's ancestors, who included many mathematicians who contributed to higher-level algebra, including George Boole, remembered best for inventing Boolean algebra.
--Dan Those who sleep faster get more rest.