46 



ASTRONOMICAL PHENOMENA AND PEOGRESS. 



more were detected in 1876, making the pres- 

 ent number 168. Coronis, No. 158, was dis- 

 covered by Dr. Knorre, of the Berlin Observa- 

 tory, on the 5th of January. Its distance from 

 the sun is 2.99, and it shines with the light of 

 a star of the llth or 12th magnitude. No. 

 159, ^Emilia, was detected by Paul Henry, of 

 the Paris Observatory, January 26th. Una, 

 the 160th of the group, was found by Dr. 

 Peters, of Hamilton College, Clinton, N. Y., 

 February 20th. It is of the llth magnitude. 

 No. 161 was first seen on the 19th of April, by 

 Prof. Watson, of Ann Arbor, Mich. The 162d 

 was discovered on the 22d of April, by Prof. 

 Henry, of Paris. M. Perrotin, of Toulouse, 

 detected No. 163 on the 26th of April. Its 

 light is not greater than that of a star of the 

 12th magnitude. The 164th of the cluster was 

 discovered by M. Paul Henry, at Paris, July 

 12th. It is of the 12th or 13th magnitude. 

 Nos. 165, 166, and 167, which have received 

 the names of Loreley, Rhodope, and Urda, 

 were discovered on the 9th, 15th, and 28th 

 of August, by Dr. Peters, of Clinton, N. Y. 

 The first two are of the llth magnitude ; the 

 last, of the 12th. Urda is the 26th member 

 of the group first seen by the Director of the 

 Clinton Observatory. No. 168 was discovered 

 by Prof. Watson, at Ann Arbor, Mich., on 

 the 28th of September. This planet is of 

 the llth magnitude, and is the 19th detected 

 by Prof. Watson. The supposed discovery of 

 another member of the group on the 28th of 

 September by Prof. Henry, of Paris, proved 

 to be a rediscovery of Maia, No. 66, which 

 had been wholly lost sight of for several 

 years. 



The name of No. 139, discovered by Prof. 

 "Watson while at Peking, was erroneously 

 given in a former volume. The Chinese name 

 selected by the discoverer is Juewa. Most 

 members of the group discovered in 1875 are 

 of the llth or 12th magnitude, and belong to 

 the exterior portion of the ring. No. 153, de- 

 tected by Palisa, November 2, 1875, and which 

 was named Hilda by Dr. Oppolzer, has a much 

 longer period than any other yet discovered. 

 Its mean daily motion, according to Dr. 

 Gchmidt, is 452", which corresponds to a 

 period of 2,865 days, or seven years and ten 

 months. This is more than double the period 

 of many asteroids in the inner portion of the 

 zone. The mean distance that of the earth 

 being unity is 3.95. The eccentricity of the 

 orbit being 0.1487, and the inclination 7 45', 

 the least distance between Jupiter and Hilda 

 will be less than one-fifth of Hilda's greatest 

 distance from the sun. At times, therefore, 

 the motion of the asteroid must be greatly dis- 

 turbed. 



The elements of several recently-discovered 

 members of the group have not yet been com- 

 puted. The mean distance, eccentricity, in- 

 clination, and longitude of perihelion, of those 

 detected since October 1, 1875, are given, so 

 far as known, in the following table : 



Saturn and his Sings. The American Jour- 

 nal of Science for June, 1876, contains an in- 

 teresting paper by L. Trouvelot on some phys- 

 ical observations of the planet Saturn. The 

 observations of Mr. Trouvelot were continued 

 through several years, and were made with the 

 fifteen-inch refractor of the Harvard College 

 Observatory, the twenty-six-inch refractor of 

 the Washington Observatory, and the six-inch 

 refractor of his own observatory at Cambridge. 

 The ring exterior to the principal division has 

 been always seen under favorable circumstances 

 to be divided into two sections by a narrow, 

 grayish line, called "the pencil-line." The 

 dusky ring, discovered by Bond, does not ap- 

 pear to be separated from the old interior ring 

 by any break or chasm. Designating the an- 

 nulus exterior to the pencil line by A, that be- 

 tween the pencil line and the principal division 

 by B, and the outer portion of the interior ring 

 by C, Mr. Trouvelot's observations show 



1. That the inner margin of the ring B, limiting 

 the outer border of the principal division, has shown, 

 on the ansagj some singular dark angular forms, which 

 may be attributed to an irregular and jagged confor- 

 mation of the inner border of' the ring B, either per- 

 manent or temporary. 



2. That the surface of the rings A, B, and C, has 

 shown a mottled or clouded appearance on the ansae 

 during the last four years. 



3. That the thickness of the system of rings is 

 increasing from the inner margin of the dusky ring 

 to the outer border of the ring C, as proved by the 

 form of the shadow of the planet thrown upon the 

 rings. 



4. That the cloud-forms seen near the outer 

 border of the ring C attain different heights, and 

 change their relative position, either by the rotation 

 of the rings upon an axis, or by some local cause, as 

 indicated by the rapid changes in the indentation oi 

 the shadow of the planet. 



5. That the inner portion of the dusky ring dis- 

 appears in the light of the planet at that part which 

 is projected upon its disk. 



6. That the planet is less luminous near its limb 

 than in the more central parts, the light diminishing 

 gradually in approaching the border. 



7. That the dusky ring is not transparent through- 

 out, contrary to all the observations made hitherto ; 

 and that it grows more dense as it recedes from the 

 planet, so that, at about the middle of its width, 

 the limb of the planet, ceases entirely to be seen 

 through it. 



8. And, finally, that the -matter composing the 

 dusky ring is agglomerated here and there into small 

 masses, which almost totally prevent the light of 

 the planet from reaching the eye of the observer. 



Comets. It is remarkable that no new tel- 

 escopic comet has been discovered since 1874. 

 This is the longest barren interval in the last 

 forty years. Some interesting researches, how- 



