ASTRONOMY AND METEOROLOGY. 843 



" Darin o^ the night of December 30, I compared tlie relative 

 brilliancy of two stars (a) and (e), marked on the maji of M. Lia- 

 pounon, in the great nebula of Orion. It is well-known that as- 

 tronomers who have especially studied this nebula, have always 

 indicated the star 6 in Orion as the most brilliant of those within 

 the nebulositj'. 



During several nights of this last autumn I remarked that the 

 star (e) shone more brilliantly than 6, Orion, which it is near. In 

 order to determine this, I placed a bi-refracting prism in the inte- 

 rior of a prismatic telescope, one metre thii-ty centimetres focal 

 length, in such a manner as to cause the double image of the two 

 stars to overlap each other. Successively alteniating the ordinary 

 Avith the extraordinary image of one of these stars, a series of 

 comparisons was obtained, which plainly showed that (e) is moi'c 

 brilliant tlian (a) or 6, Orion. As M. Otto Struye has stated that 

 there exists in this nebula a series of variable stars of feeble mag- 

 nitude, I mention the result of the preceding comparison as one 

 from which we should safely conclude that 6, Orion, was in another 

 epoch of superior brilliancy to that of (e) , which is marked in all 

 our charts as being of the fifth macrnitude. Indeed, another simi- 

 lar measure definitively established the fact that one of the two 

 stars is variable. We well know what interest attaches itself to 

 those vai-iable stars of large magnitude which are surrounded by 

 the diffused light of nebulous matter. 



" In the foregoing observations it was necessary to superpose 

 different regions of the nebula in order to eliminate the effects of 

 contrast, or of superjiosition of the luminous matter. It is almost 

 needless to say, that the intensity of the diffused light of the most 

 brilliant regions of the nebula did not attain to a hundredth part 

 of the brilliancy of fl, Orion, whilst the brilliancy of (e) surpassed 

 this last, by a quantity far greater than the value of the intensity 

 of the light emitted by the nebula." 



M. Liandier, in " Comptes Rendus," states that he watched the 

 zodiacal light in 1866, from Jan. 19 to May 5. He considers it to 

 have the shai)e of a perfect cone, varying in luminosity and color 

 from dull gray to silvery white, the changing aspect being proba- 

 bly due to the condition of our atmosphere. In February the 

 summit of the cone reached the Pleiades, and the Twins in May. 

 Between January and May he found it to follow the zodiacal move- 

 ments of the sun. He believes the luminous cone to be a fragment 

 of an immense atmosj^here enveloping the sun on all sides. If so, 

 he says it may be expected to exercise an enormous pressure on 

 the sun, with great development of heat ; and if local variations 

 occur, he thinks they may explain the occurrence of spots througli 

 the reduction of temperature that would follow diminished pres- 

 sure. 



WHAT IS A NEBULA ? 



The following ai'e the conclusions of Mr. Huggins : — 

 1. The light from the nebuke emanates from intensely heated 

 matter, existing in the state of gas. This conclusion is corrobo- 

 rated by the great feebleness which distinguishes the light from 



