SATURN. 173 



the latter is situated somewhat to the westward. This ob- 

 servation has been confirmed — partly by micrometi cal meas- 

 urements — by Harding, Struve,* John Herschel, and South. 

 The small differences in the degree of eccentricity, appearing 

 periodically, which result from the corresponding observations 

 of Schwabe, Harding, and De Vico in Rome, are perhaps con- 

 sequences of oscillations of the center of gravity of the ring 

 about the geometrical center of Saturn. It is surprising that, 

 so early as the end of the seventeenth century, a priest of 

 Avignon, nsLmed Gallet, attempted unsuccessfully to direct 

 the attention of astronomers to the eccentric position of Sat- 

 urn, t With the extremely minute density of Saturn (per- 

 haps scarcely | the density of water) and its decrease toward 

 the surface, it is difficult to form a conception of the molecu- 

 lar condition or material constitution of the body of the plan- 

 et, or even to decide whether this constitution actually pre- 

 supposes fluidity, i. e., mobility of the smallest particles, or 

 solidity, according to the frequently adduced analogies of 

 pine wood, pumice-stone, cork, or a solidified liquid — ice. 

 Horner, the astronomer of the Krusenstern expedition, calls 

 the ring of Saturn a train of clouds ; he maintains that the 

 mountains of Saturn consist of masses of vapor.$ Conjec- 

 tural astronomy exercises here an unrestricted and tolerated 

 play. Of an entirely different nature are the serious specu- 

 lations of two distinguished American astronomers. Bond and 

 Peirce, as to the possible stability of Saturn's rings, founded 

 upon observations and the analytical calculus. § Both agree 



* Compare Harding's Kleine Ephemeriden for 1835, p. 100; and 

 S*.ruve, in Schumacher's Astr. Nachr., No. 139, p. 389. 



t la the Aciis Eruditorum pro anno 1684, p. 424, is an extract from 

 the Systema PhcEuomenorum, Saturni, autore Galletio, proposito eccl. 

 Avenionensis : " Nonnuuquam corpus Saturni non exacie annuli medium 

 obtinere visum fuit. Hinc evenit, ut, quum planeta orientalis est, cen- 

 trum ejus extremitati orientali annuh propius videatur, et major pars 

 ab occidentali latere sit cum ampliore obscuritate." "Sometimes the 

 mass of Saturn appeared not to reach exactly the middle of his ring. 

 Hence it happens that when that planet is in the east, his center appears 

 nearer to the eastern extremity of the ring, and the greater part is away 

 from the western side with greater obscurity." 



X Horner, in Gehlen's Neiiem Physik. Wdrterb., bd. viii., 1 836, p. 174. 



§ Benjamin Peirce, On the Constitution of Saturn'' s Rii.g,'\u. Gould's 

 Astron. Journal, 1851, vol. ii., p. 16. "The ring consists of a stream 

 or of streams of a fluid, rather denser than water, flowing round the 

 primary." Compare also Silliman's Amer. Journal, ser. ii., vol. xii,, 

 1851, p. 99; and with regard to the superficial inequalities of the ring, 

 as well as disturbing and consequently preserving influences of the sat- 

 ellites Sir John Herschel, Outlines, p. 320. 



