52 



SCIENCE 



[N. S. Vol. XXVIII. No. 706 



The illumination was first noted at about 

 7:45 P.M. It consisted of a bright nebulous 

 band rising north of west from about twenty 

 degrees above the horizon. The light ex- 

 tended across the sky to near the north of 

 east horizon, diminishing in brightness from 

 west to east, the bands in the east and west 

 being connected by three separate bands. At 

 about 8 :15, the illumination faded, except the 

 western solid band, which persisted for about 

 ten minutes. Before it disappeared, however, 

 a series of short narrow shafts, nearly 

 parallel to one another, appeared about fifty 

 degrees above the horizon in a direction 

 slightly west of north. The eastern-western 

 illumination was steady, while the northern 

 shafts were " trembly," somewhat suggesting 

 the aurora borealis. It should be remem- 

 bered, however, that there were no lights of 

 whatever nature in the north, except these 

 detached shafts. 



It would seem plausible on first thought to 

 attribute this display to the zodiacal light, 

 or the aurora borealis, or to a combination of 

 the two. The season of the year and the loca- 

 tion of the steady glow appear to indicate 

 the zodiacal light. This is rarely seen in our 

 latitude, except near the equinoctial periods; 

 when the inclination of the ecliptic to the 

 horizon is at a maximum — and then only in 

 localities where outdoor illumination is not 

 general, and the air is unusually clear. In 

 the spring the light is first seen as a pale 

 illumination in the west, suggesting an un- 

 usual prolongation of twilight. In the au- 

 tumn, the • phenomenon, often called the 

 " false dawn," is visible before daybreak. The 

 zodiacal light is of frequent occurrence in 

 low latitudes, where the illumination some- 

 times extends across the meridian, forming a 

 secondary display in the east. At times a 

 detached luminous patch is observed in the 

 sky, about 180 degrees from the sun's posi- 

 tion. This is called the " gegenschein," or 

 " counter-glow." I can recall no authentic 

 reports of the appearance in our latitude of a 

 secondary light or the counter-glow. 



Returning to the exhibition of last March, 

 the zodiacal light hypothesis fails to account 



for the detached shafts high above the horizon 

 to the west of north. Some vpriters appear 

 to make a distinction between auroral dis- 

 plays (" fictitious " auroras, as it were), and 

 the characteristic aurora borealis. Reports 

 of the simultaneous displays of the zodiacal 

 light and auroral phenomena are matters of 

 authentic record. In the case under discus- 

 sion, there is a chance that two independent 

 phenomena were occurring at the same time, 

 but the chance was infinitesimally small. 

 Moreover, one of the most pronounced sensa- 

 tions of the beholder was that he was witness- 

 ing one phenomenon, with one cause. 



As is generally known, neither the aurora 

 borealis nor the zodiacal light has been quite 

 satisfactorily explained. The latter has been 

 variously attributed to extensions of the sun's 

 corona, to the reflection of the sun's light 

 from masses of meteoric matter revolving 

 around the sun in planes near the ecliptic, or 

 around the earth itself. Chaplain G. Jones, 

 of the U. S. Navy, who, in 1855, made a 

 particular study of the zodiacal light while 

 on duty in Asiatic waters, could not explain 

 the disposition of the light as he observed it 

 on any hypothesis other than the last men- 

 tioned. Reports have also been published of 

 the appearance of a similar band about the 

 moon. 



The main difficulty in the way of the study 

 of the zodiacal light is found in the fact that, 

 owing to the nature of the light, the telescope 

 can not be brought into service. Again, a 

 brilliant display is a rarity, except in equa- 

 torial latitudes, where observatories are very 

 scarce. If the light were due to the sun's 

 corona, its spectrum should be identical with 

 that of the solar corona, and if due to reflected 

 sunlight alone, the polariscope should show 

 that the light is polarized. Observations with 

 both kinds of instruments show conflicting — 

 or rather mixed results. 



The following hypothesis is submitted as a 

 possible explanation of the phenomenon of 

 last March, and is believed to be in line with 

 the latest theory as to the constitution of 

 matter. 



Whatever the sun's corona may be, it is not 

 a heat phenomenon pure and simple. If it is 



