Wow, this Things of Science unit really exemplifies what was best about these kits. At first blush, “Straight Line” sounds sort of dull. The “things” that came with this unit were simple pieces of a stiff paper, die-cut to length with pre-punched holes at various intervals. Additionally there were brass brads that allowed you to connect the die-cut strips into linkages. All in all, a pretty low-budget kit. But that is part of the charm….
After some history of geometric constructions and a discussion of curves, we get straight to the linkages. Several historical linkages are presented for the kit-owner to construct. These are clever geometric constructions that, while freely allowed to pivot, they nonetheless succeed in restricting some part of the linkage to linear motion. Knowing that pivoting linkages can only sweep out arcs (curves), it is a wonder that these early inventors were able to conceive of arrangements that produced lines.
I suspect if this kit had landed in the lap of young-me I would have been off on a tear trying to device my own linkages.
Here is the booklet (it lists linkage lengths if you want to create your own “things”):