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Calder's Final Triumph:

Calder's skillful positioning of Mountains and Clouds in the Hart atrium contributes to the work's success. The placement cleverly integrates the sculpture into the towering asymmetrical interior of the building, both vertically and horizontally. Calder advocated simplicity in the design of this work, since the space presents a complex background of doors, windows, balconies, stairwells, and a coffered skylight. Similarly, by selecting a matte black surface for the entire composition, he created a bold contrast to the polished white marble of the surrounding interior walls.

The aluminum clouds were raised first, spanning 75 feet and weighing more than two tons. The installation of the steel mountains followed, reaching a height of 51 feet and weighing 36 tons.

Calder intended Mountains and Clouds to be considered from multiple vantage points. Viewers can climb the mountain, in a sense, by moving up the floors. Each stage of the ascent offers different views -- indeed, different understandings -- of the mountains and clouds. As in actual mountain climbing, the distant clouds gradually become looming clouds during the ascent, until eventually the climber stands above them.

Although the mobile no longer turns today, the clouds originally rotated slowly, driven by an electrical motor installed in the ceiling.
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