ASTRONOMICAL PROGRESS IN 1900-1901. 



only 3.3 years-. Those of the shortest are called 

 Jovian comets, because when at their aphelia 

 they are at or near the orbit of Jupiter. Of this 

 class there are 22. Similarly Saturn has 3, 

 Uranus 4, and Neptune 6. The present status of 

 these periodics is doubtless due to the attraction 

 of those giant planets. The first recorded appear- 

 ance of Encke's comet was in 1786. On a subse- 

 quent return to perihelion it was rediscovered by 

 Caroline Herschel, and in 1818 it was again seen, 

 without raising a suspicion that it was the same 

 comet. Collecting the observations made in 1818, 

 Encke attempted to compute an orbit for it, on 

 the supposition that it was a parabola or an 

 hyperbola, but failed, as it seemed to be not only 

 an ellipse, but one of only three and a quarter 

 years. As the time for another return drew near, 

 he computed a finding ephemeris for it for 1822, 

 and it kept its appointment to within a few days ; 

 but unfortunately it was visible only in the 

 southern heavens, and was seen by only a single 

 person. Since then it has not been missed at a 

 single return. It is sometimes seen with a short 

 bushy tail, but generally it is tailless, appearing 

 like a faint circular. hazy disk. It is sometimes 

 visible to the naked eye. One anomalous feature 

 of the motion of this comet is that its period is 

 regularly shortening at the rate of about two 

 hours at every return. The cause of this retarda- 

 tion is unknown. It is usually, and with some 

 reason, ascribed to its encounter with something, 

 no one knows what, called a resisting medium, 

 that pervades all planetary spaces and may be of 

 infinite extent. If this theory be true, the same in- 

 fluence will ultimately cause all the planets to fall 

 into the sun. 



Brorsen's comet, due at perihelion in January 

 last, escaped detection, as is often the case with 

 short-period comets. Denning's comet also es- 

 caped detection. 



Astronomical Photography. The popular 

 as well as the scientific world view with astonish- 

 ment the advancement in this new department 

 of astronomy. The rapid plates take to a 

 great extent the place of the human eye. Daily 

 and hourly, in some part of the world, the Sun 

 is photographed, thus recording the number, 

 size, and position of his spots and pores and 

 faculae. The constellations are likewise photo- 

 graphed, bringing to view, by long exposure, stars 

 too faint for any visual telescope to see, and clus- 

 ters and nebulae whose light left them hundreds 

 and thousands of years ago. Dr. Roberts, of Eng- 

 land, who ranks high as a celestial photographer, 

 has recently published a volume of his photo- 

 graphs of various objects, such as the Sun, Moon, 

 comets, clusters, the Milky Way, and double and 

 triple stars, which is very valuable. A more 

 wonderful or interesting story has seldom been 

 presented to the world than the marvelous revela- 

 tions of what the great Crossley 3-foot photo- 

 graphic telescope at Lick Observatory has done 

 in celestial photography, as manipulated by the 

 late Prof. Keeler. His photographs of the ring 

 nebula in Lyra, the annular nebula in Cygnus, the 

 famous cluster of stars 13 Messier in Hercules, the 

 great nebula in Andromeda, and many other in- 

 teresting objects, reveal much that was formerly 

 unknown. Happening to expose one of Dr. Swift's 

 faint nebula, he found that it was spiral. A com- 

 parison of these photographs with those to be 

 taken centuries hence may decide many questions. 



At Harvard Observatory, in the last two and a 

 half years, 10,000 photographs have been taken. 

 By an exhaustive examination of the plates it was 

 found that the famous asteroid Erbs, now attract- 

 ing so much attention, appears on 15 charts taken 



before it was discovered by Witt, and on 5 spec- 

 trum plates between October, 1893, and May, 1894, 

 and on 6 plates in 189(5. On one of the plates 

 8 asteroids were depicted, and on another 46 

 new nebulae were counted. Prof. Keeler discov- 

 ered 7 new nebulae on a photograph plate that 

 had been exposed to the well-known nebula 51 

 Messier, all on one square degree. On a plate 

 exposed four hours on one of Herschel's nebula 

 in Andromeda, 36 new nebulae and nebulous stars 

 were found, and on another 20. All these had 

 escaped Sir William Herschel's eye and telescope. 

 Besides the nebulae, there was often found a con- 

 siderable number of objects which are probably 

 nebulae so small that the resolving power of the 

 great 36-inch telescope is insufficient to define 

 their true character. 



Dr. Isaac Roberts has found by photography a 

 very remarkable nebula in Monoceros, which is 

 well worthy of study. A black gap or hole is 

 in the center, resembling a dark tunnel through 

 which everything beyond is of inky blackness, in 

 appearance totally unlike any other known 

 nebula. 



These citations are sufficient to show how 

 photography, by long exposure and rapid plates, 

 reveals objects far beyond the powers of any tele- 

 scope. The Milky Way, that mighty Gulf Stream 

 of stars, is made up of the silver light of hundreds 

 of millions of suns, only a few of which will ever 

 be visually seen by any telescope. 



Astronomical Prizes. The following astro- 

 nomical prizes since the last report have been 

 awarded to astronomers for meritorious work in 

 its several departments: 



The Laland prize, of a silver medal and 540 

 francs, was awarded by the French Academy of 

 Sciences to M. Giacobini, of the Nice Observatory, 

 for the discovery of comets (a), Jan. 31, 1900, 

 and (c) of Dec. 20, 1901. 



The Damoisean prize was awarded to J. von 

 Hepperger, Professor of Astronomy at Graz, for 

 investigations into the motions of Biela's comet 

 at its separation into two separate comets at its 

 return in 1846, resulting in the production of the 

 two Andromeda star showers of Nov. 26 and 27. 



The Valtz prize was given to Abbe Verechaffel, 

 of the Abbadia Observatory, for extensive star- 

 zone work. 



The Janssen prize, a large gold medal, was 

 awarded to Dr. Edward E. Barnard, now of 

 Yerkes Observatory, for the discovery, in 1892, of 

 Jupiter's fifth satellite. 



The Gold Medal of the Royal Astronomical 

 Society of England was bestowed on Prof. Ed- 

 ward C. Pickering, director of Harvard College 

 Observatory for extensive astronomical research. 



The same society presented a cash prize of 1,000 

 guineas to Sir William and Lady Huggins, for 

 distinguished services to astronomy. 



Beginning with 1823, the Royal Astronomical 

 Society of London has, with a few exceptions, an- 

 nually awarded a gold medal for conspicuous 

 originality and research, in whatever country 

 they might be shown; and the honor is height- 

 ened by the fact that occasionally it has voted 

 to give no medal at all. For forty-two years no 

 award was made outside of England and the Con- 

 tinent of Europe, and it was only in 1865 that the 

 medal first came to this country, twenty years 

 after the establishment of the first American ob- 

 servatory. The recipient was Prof. George P. 

 Bond, director of Harvard Observatory, a son of 

 Prof. William C. Bond, former director of the 

 same observatory. Nine years later the same 

 honor was conferred on an American astronomer, 

 Prof. Simon Newcomb, of Washington, whose 



