Todd compared the Aeroscope to Paris's Eiffel Tower and Chicago's Ferris Wheel. It was the invention of J. B. Strauss of Chicago, head of the Strauss Bascule Bridge Company, and in effect it was one leaf of a bascule bridge stood on end. A steel arm reached 200 feet beyond its pivots and carried a two-story cab for 120 people. Behind the pivots a shorter arm ended in a 380-ton counterweight of steel and concrete. The pivots sat on a steel tower 48 feet high. The tower's round base rode on railway trucks around a circular track 60 feet across.
A clever trick kept the arm balanced. Water tanks under the cab let out each boarding passenger's exact weight in water and pumped it back when he stepped off. Balanced that way, the arm needed little power to rise. Once the cab cleared the neighboring tall structures, gears began turning the whole tower, so the cab climbed in a great spiral and faced every point of the compass. At the top riders were 265 feet above the ground and, because the site itself stood about 65 feet up, some 330 feet above the sea. From there they could see into seven counties and far out over the Pacific. A trip took about ten minutes. Aeroplane propeller blades on the cab's sides steadied it. Todd thought they also helped the picture.
Erection began on October 25, 1914, and the first run was on February 12, 1915, days before the fair opened. It was a marvel but not a business. It took in over $67,000 and had cost almost that much to build, and Todd blamed a poor location with an inconspicuous approach. Strauss went on to greater fame: he is credited as chief engineer of the Golden Gate Bridge, though Charles Alton Ellis did most of its structural design.
Paris had its Eiffel Tower and Chicago had its Ferris Wheel, but the Zone at San Francisco had something that combined a little of both, and in some ways was more interesting than either.
Frank Morton Todd, The Story of the Exposition, vol. 2, p. 151 (1921)
