ZODIACAL LIGHT. 129 



the western horizon, and at the end of autumn, before the 

 commencement of morning twilight, above the eastern 

 horizon. 



It is difficult to understand how so striking a natural 

 phenomenon could have failed to attract the attention of 

 astronomers and physical philosophers before the middle of 

 the seventeenth century, or how it should have escaped the 

 observant Arabs in ancient Bactria, on the Euphrates, and 

 in Southern Spain. We are almost equally surprised at the 

 late period at which the nebulse in Andromeda and Orion, 

 first described by Simon Marius and Huygens, were ob- 

 served. The earliest distinct description of the Zodiacal 

 light is contained in Childrey's Britannia Baconica( 91 ), of the 

 year 1661 ; its first observation may have been two or three 

 years earlier. Dominic Cassini has, however, incontestably 

 the merit of having been the first (in 1683) who investi- 

 gated its relations in space. The luminous appearance 

 which was seen by him in 1668 at Bologna, and at the same 

 time in Persia by the celebrated traveller Chardin (and 

 which the Court astrologers of Ispahan, who had never seen 

 it before, named " nyzek" or " small lance"), was not, 

 as has often been said, the Zodiacal light, but the enormous 

 tail of a comet ( 92 ), the head of which was concealed by its 

 proximity to the horizon, and which, in its position and 

 appearance, presented many points of resemblance to the 

 great comet of 1843. But it may be conjectured with 

 much probability, that the remarkable light rising pyrami- 

 dally from the earth, which, in 1509, was seen in the 

 eastern part of the sky for forty nights in succession from 

 the high table land of Mexico (and which I found men- 

 tioned in an ancient Aztec manuscript, in the Codex 



