Le Soleil. [2 volumes + Atlas].

Paris:: Gauthier-Villars, 1875, 1877., 1875. 2 volumes + Atlas. Tall 8vo. xx, 428; viii, 484 pp. Atlas: [iv], 6 engraved double-page plates. 13 plates, 280 figs. (some in color). MEMORIAL BOOKLET BOUND IN: Padre Angelo Sechi (In More del Padre Angelo Secchi, Canto Dell'Avvocato B. Mattiauda. Roma: Tipografia Delle Scienze Matematiche e Fisiche, 1878.14 pp). Later half maroon gilt-stamped morocco, marbled boards, raised bands, top edge gilt, initials of owner on foot of spine. Signatures and armorial bookplates of Samuel Verplanck Hoffman. Very good. Second edition. "By observing sunspots at various solar latitudes, Secchi determined that the Sun had a differential rotation and behaves more like a liquid than a solid body. He named the bright areas around sunspots 'faculae', deduced (correctly) that solar granulation was attributed to the action of convection cells, and measured the effect of limb darkening. / Secchi's solar studies were summarized in Le Soleil, published in 1875-1877, in which Secchi related the observed surface phenomena to an overall model of the Sun's structure. He took the Sun to be composed mainly of gas and subject to complex circulation, with surface eruptions driven by an unrecognized force (later found to be magnetic fields)." – Thomas Hockey, Biographical Encyclopedia of Astronomers, p. 1040. / "Angelo Secchi, an Italian astronomer, died Feb. 26, 1878, at age 59. Secchi was a Jesuit and spent most of his life with the Observatory of the Roman College in Rome, serving as its Director from 1850 until his death. Secchi observed the planets and stars from the roof of the Church of St. Ignatius, which gives the term "study of the heavens" a rich double meaning (second image). Secchi is best known for his work in solar and stellar spectroscopy. Spectroscopy had been founded in 1859, with the discovery that the dark lines in the solar spectrum could be used to identify the elements in the sun. Secchi expanded spectroscopy to include the stars, whose spectra were much more difficult to observe. Secchi discovered that stars come in different "spectral types," with some stars, like the Sun, having many dark lines, while others, like Sirius and Vega, have many fewer lines. He identified four kinds of stars, which he called Types I, II, III, and IV (third image). These designations would be used until they were superseded by the OBAFGKM system proposed at Harvard around the turn of the 20th century. Secchi's stellar types were illustrated by attractive chromolithographs in his book Le Soleil (1870) . . . the second French edition (1875) and the first German edition (1872)." – Linda Hall Library – Dr. William B. Ashworth, Jr. PROVENANCE: Samuel Verplanck Hoffman (1866-1942) graduated from Harvard with a degree in mechanical engineering, and from Johns Hopkins with a graduate degree in astronomy, however he devoted most of his life to managing his father's extensive properties in New York City. He was a member of the New York Historical Society for over 40 years, serving as president from 1903 to 1913.