One must wonder what were Solon Bailey's feelings when, on February 25, 1893, he found himself once again in Arequipa, Peru, in charge of Harvard's astronomical station there. The site was one he had chosen two years earlier after exhausting years of exploration, and which he had hoped would yield great results. Instead, in the intervening two years the station had been in the hands of William Pickering, brother of the Harvard Observatory's director, Edward Pickering. William had completely wasted the station's resources and brought great disrepute to Harvard's work there. Now Bailey had to again take over, William having been—with considerable difficulty—recalled to Cambridge.
It was a daunting task. Bailey found the station close to ruin, both financially and in its equipment. Assistants and servants had been given carte blanche to run up bills in the town. William and his family had not stinted themselves either. Telescopes were grossly maladjusted, owing to William's attempts to adapt them to purposes for which they were not designed. The seismograph recorded a major earthquake every time the door to its room was opened, some weather instruments had never been set up, and the all-important clocks were seriously unreliable, some with parts missing.
Bailey was equal to the task. Under his wise and firm leadership, the station slowly regained its stability and its good working order. The golden years of astronomy in Arequipa finally began. The main work was to photograph the Southern skies (repeatedly in interesting areas) with various instruments and thereby to derive the positions, magnitudes and spectra of stars and other objects. It must have seemed dull, routine work to many, but it led to some of the most profound developments in astronomy during the 20th century. It was photographs from Arequipa, for example, that led to the discovery of the Cepheid period-luminosity law, a cornerstone of modern cosmology.
One thing Bailey decided against, however, was observing Mars at another of its nearer passages. On the previous such occasion William Pickering, using the Arequipa equipment, had claimed in widespread newspaper reports the most absurd results about lakes and canals on Mars. Writing with some irony to Edward Pickering, Bailey reported:
I have given very brief attention to Mars. I have concluded that my time will be better spent in other lines, especially as the northern observatories will doubtless give so much attention to it and see all there is to be seen, if not more, and also I fear that I have not the creative faculty sufficiently developed to make a mark as an observer of Mars.
Instead Bailey turned his attention to meteorology. The main reason was that the money used to run the Arequipa station had come from the Boyden Fund, a gift that the donor had stipulated must be used to fund an astronomical observatory at a mountainous site above lower-level atmospheric disturbances. Arequipa, at an elevation of not much over 2,400 meters, barely qualified as such, especially with the Andes towering nearby. Was there a better site at a higher elevation not far off? Bailey soon found the question could not be immediately answered, because Peru then lacked almost any systematic meteorological data. He therefore determined to set up an array of roughly east-west weather stations running from Mollendo on the Pacific coast right across to the eastern side of the Andes, some in valleys, others on mountains.
More easily said than done! Bailey noted in one of his reports: "In Peru, outside of one or two large towns, there are no highways suitable for vehicles of any kind. Travel and traffic, except that done by the few railways, are carried on entirely on the backs of horses, mules, donkeys, and llamas."
But characteristically there was no question of Bailey staying in Arequipa while others did the hard work. Although now in his 40th year, Bailey was soon out on horseback getting things done. As his obituarist would eventually note,
... there were adventures such as swinging from peak to peak over a deep valley in a cage suspended by a single cable, or descending rapidly from elevations of 10,000 feet in a hand car with gravitation as the motive power, or passing nights on desolate mountains where perhaps the only sounds were the "ripple of the [river] far below, and the flapping of the condor's wings".