ley's which should be referred to here, were it not for limited space. His observations on the moon's heat; on the solar eclipse of 1878 (at the summit of Pike's Peak); his direct comparison of the sun with the molten metal of a Bessemer converter; his investigations at Mount Etna, Pike's Peak, and Mount Whitney, on the conditions of vision at great altitudes, all deserve more than this brief notice.
His published scientific papers are very numerous. A list of the more important of these follows this article. There are forty-six separate papers in the years from 1869 to 1885. Besides these, the magazines have contained many more popular articles; and his courses of lectures at the Lowell Institute, the Peabody Institute, and elsewhere, have been most successful.
Professor Langley is a member of the National Academy of Sciences and of numerous American and foreign bodies, and has received the recognition of honorary degrees from various universities.
| No. | Date. | Title or subject. | Where published. |
| 1 | August, 1869. | Eclipse of August 1869. | "United States Coast Survey Reports." |
| 2 | December, 1869. | Proposed Plan of Time-Service. | Pittsburg. |
| 3 | January, 1871. | Eclipse Expedition of 1870. | "Nature," January, 1871. |
| 4 | February, 1871. | A New Form of Solar Eyepiece. | "Franklin Institute Journal," February, 1871. |
| 5 | April, 1871. | Observations on Eclipse of 1870. | "United States Census Reports." |
| 6 | September, 1872. | American System of Electric Signals. | "American Journal of Science" November, 1872. |
| 7 | August, 1873. | The Solar Photosphere. | "Proceedings of the American Association," 1873. |
| 8 | February, 1874. | Minute Structure of Photosphere. | "American Journal of Science," February, 1874. |
| 9* | Aug. & Sept., 1874 | External Aspects of Sun, with Typical Sun-Spot Plate. | "Franklin Institute Journal," August, 1874. |
| 10* | September, 1874. | Photosphere and Sun-Spots. | "Popular Science," September. |
| 11* | December, 1874. | Transit of Venus. | "Popular Science," December. |
| 12* | March, 1875. | Sources of Solar Heat (lecture) | "New York Tribune," Mar. 10. |
| 13 | March, 1875. | Comparison of Theory and Observation | "American Journal of Science," March. |
| See, also, Memorie degli Spettroscopisti, Typical Sun-Spot Plate with each Memoir. | |||
| 14 | March, 1875. | Temperature Relative des etc. | "Comptes Rendus," Mar., 1875. |
| 15 | September, 1875. | Radiations Superficielles de Soleil. | "Comptes Rendus," Sept., 1875. |
| 16 | September, 1875. | The Solar Atmosphere. | "American Journal of Science," 1875. |
| 17 | November, 1876. | Effect of Sun-Spots on Terrestrial Climate. | "Royal Astronomical Society Notices," November. |
| 18* | April, 1877. | The first "Popular Scientific Treatise." | "Popular Science," April, 1877. |
| 19 | May, 1877. | Nouvelle Methode, etc. | "Comptes Rendus," May, 1877. |
| See, also, "American Journal of Science," August, 1877. |
