The opening of Baldwin's tetrahedral tower in Nova Scotia, 31 August 1907. The designer was Frederick 'Casey' Baldwin, assisted by his boss Alexander Graham Bell. Both were members of the Aerial Experiment Association, and were investigating new engineering structures for possible future use in aeroplanes. The tower was intended to demonstrate the strength of the new concept which relied on a series of interlocking equilateral triangles in the form of regular tetrahedrons. The concept did not become very popular until the mid-20th century, too late for either Baldwin or Bell to witness.