Free: scanned copy of Martin Gardner's Logic Machines and Diagrams (1958)

I love Martin Gardner's puzzle, math, magic, and philosophy books. I just learned from visiting Clifford Pickover's website about a Gardner book that's new to me: Logic Machines & Diagrams (1958).

From the introduction:

A logic machine is a device, electrical or mechanical, designed specifically for solving problems in formal logic. A logic diagram is a geometrical method for doing the same thing. The two fields are closely intertwined, and this book is the first attempt in any language to trace their curious, fascinating histories.

I think I need the hard copy.