162 Prismatic Spectra of the August Meteors. 



on the 13th of November will, doubtless, show a different 

 result. The streaks of the November meteors are quite as 

 enduring as those left by meteors on the 10th of August ; but 

 their colour is white, verging to blue, while a glance at the 

 brightest and most enduring meteor- streaks left on the 10th 

 of August generally shows their yellow cast of colour. The 

 first, or rudimentary colour of the August meteor- streaks is, 

 like that of the November streaks, white or bluish ; and some 

 few continue of this colour until they disappear. The effect 

 is owing to the ignited vapour of the other mineral substance 

 (potassium, sulphur, or phosphorus) to which allusion was 

 just made, playing a principal part in the production of the 

 streaks. Although glowing for a much shorter time, and 

 with less intensity than the vapour of the metal sodium, it 

 nevertheless in some instances forms the entire light of the 

 meteor- streaks seen on the 10th of August. White, bluish, 

 or "phosphorescent" streaks are most prevalent among the 

 November meteors, and the light of this element, whatever 

 it be, by which this bluish kind of phosphorescence of the 

 •streaks is produced, will probably appear more highly deve- 

 loped, and its spectrum will be more easily identified in the 

 streaks of the meteors on the 13th of November, than it could 

 be (from the brightness of the sodium-line) in the enduring 

 streaks of the meteors of the 10th of August last. It extends 

 between the red and the blue ; and is that portion of the visible 

 train-spectrum which is called " diffuse" in the following 

 observations : — 



The meteor spectroscope, as already described, presents to 

 the view a pretty considerable extent of the star-spangled 

 surface of the sky. The spectra of the well-known " seven 

 stars" of Ursa Major, may, for example, be seen together in 

 the instrument at a glance. Each bright star is converted 

 into a line of highly-coloured light, nearly three-quarters of a 

 degree in length ; and horizontal, when the instrument is held 

 in its natural position. Fifth magnitude stars are obliterated, 

 and fourth magnitude stars appear only as a greyish line of 

 light of no decided tint or colour. Prismatic hues are first 

 perceptible in stars of the third magnitude and upwards. When 

 the spectroscope is turned to a given part of the sky, the stars, 

 through it, appear as if a gigantic wet brush, had been applied 

 to them in that part of the sky, and their light had been par- 

 tially washed out in a particular direction. The effect is pro- 

 duced by the dispersion of the light of each star in passing 

 through the prisms. Its single beam is spread out, as it were, 

 into a fan of different coloured rays, called its "prismatic 

 spectrum," and its light is proportionately enfeebled j but the 

 stars appear to occupy very nearly the same relative positions 



