36 



ASTRONOMICAL PROGRESS IN 1902. 



comb, right ascension 18 h 28 n >, declination north 

 35, or near Alpha Lyra. Kapteyn, right ascen- 

 sion 18> 16m -|- 20, or in Hercules. Campbell 

 Igh 28n-f-20; velocity 12.4 miles a second. 



To elucidate the spectroscopic process by 

 which it is hoped the direction of the Sun's mo- 

 tion may be determined the following facts must 

 be borne in mind. If a star is not moving 

 toward or from the solar system, or we toward 

 or from the star, the spectral fines of hydrogen, 

 sodium, iron, etc., will occupy precisely the same 

 positions that are experimentally observed in the 

 chemist's laboratory. If the lines in the spec- 

 trum of the star occupy positions slightly toward 

 the red end of the spectrum, that star is either 

 moving from the Earth or the Earth from the 

 star, or both from each other. On the other 

 hand, if all the lines are moved slightly toward 

 the violet, that star is either moving toward the 

 Earth or the Earth toward the star, or both to- 

 ward each other. If the lines from all the stars 

 in a certain region of the sky are moved toward 

 the violet, it furnishes strong evidence that the 

 Sun with his family of planets is moving in that 

 direction, or that all the stars in the region are 

 moving in our direction an improbable suppo- 

 sition. 



If the spectral lines from stars in a certain di- 

 rection are moved toward the violet the theory 

 demands that the lines from stars in the opposite 

 direction shall be displaced toward the red. 



The Zodiacal Light. The cause of this 

 strange light is one of the most inexplicable mys- 

 teries of the heavens. It is very doubtful if its 

 cause will ever be discovered. It is gratifying, 

 however, to announce that it is beginning to at- 

 tract the attention it. deserves. For its investi- 

 gation no instrument, unless it be the spectro- 

 scope, can be used. Though the area of the light 

 is large, it is too faint for telescopic observation, 

 and the hope that the spectroscope can deal in- 

 telligently with it is almost a forlorn one. So 

 faint is it that the light from the planets Venus 

 and Jupiter are sufficient to obliterate it. It is 

 also too faint to attract popular attention, but 

 none the less necessary to be investigated. It is 

 a broad beam of light, seen in the west above 

 the place where the Sun has set as soon as twi- 

 light is ended, and in the morning sky before 

 dawn appears. It is conical, 25 degrees broad 

 at the horizon, and extends often to near the 

 zenith, where it narrows to a blunt point. Some 

 observers think they have seen it extend from 

 horizon to horizon. In some countries it is seen 

 only during the 3 spring and autumnal months, 

 in the west in spring, and in the east in au- 

 tumn. This, if true, is an important fact as 

 associated with the meteoric-ring hypothesis. At 

 the Lowe Observatory, in southern California, 

 3,500 feet above tide-water, it is visible the year 

 round in the west; but, owing to obstruction 

 by the San Gabriel mountains, it is never seen 

 in the east except from the top of Mount Lowe, 

 one of its highest peaks. 



Several plausible theories have been advanced 

 to. explain the cause of this light, but in the 

 writer's opinion they are not worth recording. 



The writer is of the opinion that the zodiacal 

 light is due to the reflection of sunlight from the 

 cast-off tails of comets. No comet gathers its tail 

 to itself; a part is left behind, and the process 

 has boon going on since the creation. This hy- 

 pothesis demands that the cometic ring extend 

 far beyond the earth, if not to Neptune's orbit, 

 its eccentricity being very great. 



The Gegenschdn is another mysterious light, 

 in several respects more so than the zodiacal 



light, with which it seems to be associated. Prof. 

 Barnard has made it a systematic study for 

 fifteen years. It is a circular light, always ex- 

 actly opposite the Sun, therefore on the meridian 

 at midnight. He has traced what he calls the 

 zodiacal band, extending from it to the evening 

 and morning zodiacal cones, 3 or 4 degrees broad, 

 and it can be seen, except where it crosses the 

 Milk}' VVay, in June and December. The writer 

 never saw it in New York, but in California was 

 surprised at its brilliance. 



Mercury. The exact diameter of Mercury 

 has always been considered beyond the limits of 

 accurate measurement. Recently, from a long 

 series of micrometer determinations with the 26- 

 inch telescope at the Naval Observatory, Prof. 

 T. J. J. See has deduced a mean diameter of 

 5.8993", with a probable error of only 0.0080". 

 There was no appearance of an atmosphere or 

 evidence of any markings on his disk. This 

 gives the diameter of the planet about 3,000 

 miles. 



Jupiter. Prof. See has recently completed a 

 series of daylight observations to determine more 

 reliable values of Jupiter's diameter with the 

 same telescope. They were made when he was at 

 the distance of 5.20 (the Earth's distance from 

 the Sun being 1) with the following result: 

 Equatorial diameter 37.646", polar 35.222", cor- 

 responding to 88,151 and 82,475 miles respect- 

 ively. Since last report Prof. See has subjected 

 Saturn and his rings to a long series of micro- 

 metrical measurements with the following re- 

 sults: Equatorial by night, 76,598; by daylight, 

 74,172. External diameter of outer ring, 171.948. 

 External diameter of dusky ring, 111,969 miles 

 respectively. 



Bolides. Since the last report several of 

 these strange celestial visitors have suddenly ap- 

 peared and as suddenly vanished where from 

 and where gone is a fathomless mystery. They 

 are also called fire-balls and meteors. That they 

 are identical with the fall of meteoric stones 

 is generally conceded; but that they are even 

 remotely connected with what are called shoot- 

 ing stars is in the highest degree improb- 

 able. During the great star showers of Nov. 

 13, 1833, and the 14th in 1866 not a bolide was 

 seen, though countless millions of the micro- 

 scopic meteors were seen over a large portion of 

 the earth. No shooting star ever has been known 

 to reach the Earth. The writer well remembers 

 the celebrated one of 1860. In Niagara County, 

 New York, he rose to give a lecture, when in- 

 stantly the room was lighted to the brilliance 

 of a sunny day, and the light disappeared as 

 quickly as a flash of lightning. It was first seen 

 in Colorado in broad daylight, and last seen 

 over the Atlantic Ocean. Whether it ever 

 reached the Earth is not known. Its velocity was 

 from 12 to 15 miles a second. 



The object in calling the reader's attention to 

 this subject is to describe the appearances of 

 3. among several others, on as many different 

 dates which have appeared in the past twelve 

 months. On Dec. 16, 1901, a remarkably bright 

 one was seen in England, in the constellation of 

 Perseus. It moved north almost at a right angle 

 to the ecliptic, and disappeared beneath the pole- 

 star. On Nov. 13, 1901, one was visible over a 

 large portion of England. Its path remained vis- 

 ible a short time when a dotted streak of light 

 appeared, finally assuming a faint nebulous 

 cloud. The most remarkable of the three passed 

 over New South Wales at 9 h 35 m on the even- 

 ing of Jan. 7, 1902, visible over a region 300 

 miles in length. It first appeared in the con- 



