ALS signed “N. Tesla,” four pages on two adjoining sheets, 5.75 x 6.75, personal monogram letterhead, May 18, 1899. Handwritten letter to Rear Admiral Francis J. Higginson by Nikola Tesla, from the Alta Vista Hotel in Colorado Springs, in part: "My coming here was necessary because I wanted to obtain some data in high altitudes in view of my attempt to communicate with and possibly to transmit energy to Europe. These data though they are for a different purpose will also be useful in telegraphy. The work here will keep me working three to four weeks, but on my return I shall immediately devote as much of my time as possible to the task of establishing a thoroughly satisfactory and reliable communication with the lightship." In very good to fine condition, with light staining to the right side.
In May, Higginson had written to Tesla on the subject of wireless telegraphy, asking if he would be able to develop a system to be deployed on Light-Vessel No. 66, Nantucket Shoals, Mass., lying about 60 miles south of Nantucket Island. At the time, Tesla had patents pending on basic radio technologies, which would be granted in 1900. In spite of Tesla's initial interest, the plan would not come to fruition—the Navy refused to finance the project, and also found Tesla rather difficult to work with. Higginson continued to advocate for wireless communications technology within the government, and in 1901 Marconi wireless telegraph equipment was 'temporarily and experimentally installed' on the Nantucket lightship. In 1904, it would become the first US lightship to be permanently equipped with radio—though not of Tesla's design.
Nikola Tesla had arrived in Colorado Springs earlier in May, and he spent the summer conducting experiments related to both wireless telegraphy and power transmission. It was during this period that he reported hearing unusual, rhythmic sounds from his receiver. In a letter to Julian Hawthorne, Tesla contended that these signals were evidence that 'intelligent beings on a neighboring planet' must be scientifically more advanced than Earthlings. It has since been hypothesized that Tesla may have intercepted Marconi's European experiments in July 1899—Marconi may have transmitted the letter S (dot/dot/dot) in a naval demonstration, the same three impulses that Tesla hinted at hearing in Colorado—or signals from another early experimenter in wireless transmission. In any event, this is a significant handwritten letter by Nikola Tesla, penned during one of his most influential and productive periods of experimentation.