12 SIMON NEWCOMB— CAMPBELL. '""""roSSro 



The published descriptions of the zodiacal light had referred to it as an illumination, len- 

 ticular in form, extending east and west from the sun, but said little or nothing concerning the 

 radius of the illumination in the north and south direction. It occurred to Newcomb that the 

 latter constant could be determined by direct observation from a moderately high mountain 

 summit correctly situated as to latitude and possessing transparent sky and unobstructed 

 northern horizon. In the Northern Hemisphere the observations could best be made from points 

 whose latitudes were such that the midnight sun would be only a little more than 18 degrees 

 below the north point of the horizon, as this would eliminate the twilight effect and let the 

 zodiacal illumination extend to its highest practicable altitude. Newcomb endeavored to make 

 these observations from points in the White Mountains in several summers, but failed on 

 account of imperfect atmospheric conditions. On a later trip to Switzerland he ascended the 

 Brienzer Rothorn, altitude 7,700 feet, latitude 47°, with these observations in mind, and he was 

 successful, on the nights of July 26 and 29, 1905. The zodiacal light arch was well seen and 

 unmistakable, and it extended 35° north from the sun. A few years later these observations 

 were repeated and Newcomb's results substantially confirmed by Fath at Mount Hamilton. 



Newcomb's great program concerned the solar system, but his interests and contributions 

 extended also to the stellar system. In 1902 he published an important volume on The Stars— 

 A Study of the Universe. Its 20 chapters treat of such subjects as the proper motions of the 

 stars, the parallaxes of the stars, double, triple and multiple star systems, the apparent distri- 

 bution of the stars in the sky, the distribution of the stars in space, the structure of the Milky 

 Way, the extent of the universe, etc. 



Prof. Newcomb found time to write several admirable textbooks on astronomy. His 

 Popular Astronomy, a comprehensive treatise of the fundamental principles of astronomy, 

 issued in 1S78, has perhaps never been equaled in merit by any other book aiming to cover 

 approximately the same ground. Notwithstanding the tremendous advances of the past 40 

 years in astronomical science, the original edition remains a book which all students of astronomy 

 could read with profit and pleasure. It has passed through several editions in this country 

 and it has been translated into half a dozen foreign languages. 



An excellent Astronomy for High Schools and Colleges, written by Profs. Newcomb and 

 Holden, passed through several editions. The larger work was abridged for the use of schools. 



Newcomb published a volume on Astronomy for Everybody, a Popular Exposition of the 

 Wonders of the Heavens, in 1907, which was very successful. It has been translated into many 

 languages. His Side-Lights on Astronomy and Kindred Fields of Popular Science, which 

 appeared in 1906, reproduces 21 of his principal essays and addresses. His volume, A 

 Compendium of Spherical Astronomy, published in 1906, treats admirably of the subjects 

 which relate to the determination and the reduction of the accurate positions of the stars — 

 precession, nutation, aberration, proper motion, parallax, refraction, systematic errors of star 

 catalogues, etc. 



Newcomb possessed the power of writing for the intelligent public. Dozens of his articles 

 on subjects of timely interest, admirably conceived and composed, appeared in Harper's Maga- 

 zine, The Atlantic Monthly, McClure's Magazine, Popular Science Monthly, etc. He con- 

 tributed frequently to The Nation, The New York Tribune, The Independent, The Youth's 

 Companion, etc. Short articles and notes from his pen are numerous in Science. He wrote 

 many of the articles on astronomical subjects in the leading encyclopaedias. He made notable 

 addresses on occasions of great astronomical interest, such as the dedication of the Flower 

 Observatory of the University of Pennsylvania, the Yerkes Observatory of the University of 

 Chicago, and the Observatory of Syracuse University. 



Newcomb's interest in the progress of mathematics was strong throughout his life. While 

 an assistant on the Nautical Almanac at Cambridge he contributed frequently, especially on 

 the theory and practice of probabilities, to Runkle's Mathematical Monthly during the three 

 years of its existence. He and W. P. C. Bartlett and T. H. SafYord were the committee, appointed 

 by the editors, to judge of the solutions offered for problems set by the Monthl}-, and to award 

 prizes. 



