July 2018 36 WHEN ARIZONA WAS ON THE CUTTING EDGE OF SOLAR TECHNOLOGY Nobody was trying to do research and development of solar water heaters here. Nor were they experimenting with photovoltaic cells to generate electricity from sunlight. These pioneers into solar study were looking for a link between the energy of the sun and the weather on Earth. Today, the studies made atop the Harquahalla between 1920 and 1925 are undoubtedly gathering dust back in the Smithsonian or somewhere, having been far surpassed by modern scientific inquiry. But for a while, Arizona had its “moment in the sun” so far as solar was concerned. There was, in those days, a professor of physics and director of the Western University of Pennsylvania Allegheny Observatory named Samuel Langley. Langley believed changes in the Earth’s climate were generated by the sun. He wanted to measure these changes as a means of forecasting weather. The good professor came up with a unit of measure, called “the solar constant.” His first expedition to measure the solar constant was in 1881 when he traveled to Mount Whitney in the California Sierras for the purpose. Then, in 1887, he left the Allegheny Observatory to take a position at the Smithsonian Institution in Washington, D.C. as the third secretary. Langley packed his interest in the solar constant with him to Washington, where, in 1902, he established the Smithsonian’s Astrophysical There was a time, some 70 years ago, when Arizona was on the “leading edge” of solar technology. The site was a solar lab atop the Harguhalla Mountain on a massive ranch that runs between Aguila and Wenden on the south side of Hwy Observatory (APO). The charter of the APO mandated continued measurement of the solar constant. In 1895, a young physicist from MIT named Charles Abbot went to work at the Smithsonian and became Langley’s protégé. Just before Langley retired, Abbot became director of APO. Solar constant measurements continued under Abbot and were made from the Smithsonian between 1902 and 1907. But Washington was not a suitable location for such measurements and a clear mountaintop was needed. In 1905, Abbot accepted an invitation from George Hale to take solar constant measurements atop Mount Wilson above Los Angeles where Hale was building a 100- inch telescope. Abbot took solar measurements from Mount Wilson from 1905 until 1920. Comparing data taken from Mount Wilson, Mount Whitney, a station in Algeria and a balloon over Omaha, Abbot came to the conclusion he needed two stations widely separated to observe noted fluctuations in the solar constant measurements. By 1920 atmospheric conditions at Mount Wilson were becoming unsuitable for his purposes. Simultaneously with the establishment of a location in the mountains of Chili, Abbot personally moved the equipment from Mount Wilson to Harquahalla Mountain above the sparsely populated town of Welden, Arizona. The Harquahalla site was selected from a list of suitable suites provided by the weather bureau which also included Bagdad, Arizona and Cima, California. The weather bureau had concluded that of the three sites, the Harguahalla Mountain was “one of the most cloudless areas in the world.” Abbot requested that Congress appropriate $25,000 to build a first-rate solar constant measuring station atop Harquahalla Mountain. Congress had no interest in the project and denied his request. A private citizen came to the rescue of the Harquahalla project. John Roebling, chief heir to the Roebling Iron Works fortune and a son of the family who built the Brooklyn Bridge was a constant benefactor of the APO. He came up with $11,000 for Abbot's project. Abbot went to Wenden in 1920 and reported that the town below the mile-high Harquahalla had no more than 30 houses and three stores and “the people were very friendly and interested in the project.” He said that one store owner, a man named Bunker, was building a 25 room concrete hotel and the contractor, a man named Turner, was