The doming Meteor Shower. — The Spectra of Meteors. 39 



of the light rays through the prism. When a pencil of light 

 enters the prism, it is refracted, and then continues its course 

 until it meets one side of the prism, which it strikes at such 

 an angle that it cannot get out. It is therefore reflected to 

 another side, also at an angle which prevents its egress ; and 

 accordingly it undergoes a second reflection, after which it is 

 permitted to emerge in a position opposite, and parallel to, its 

 line of entry. 



In employing an ordinary spectroscope, it is necessary to 

 limit the admission of light by a slit. But if the source of 

 light took the shape of a fine line, no slit would be required, 

 because the mass of light would not exceed the quantity with 

 which the spectroscope could advantageously deal. With 

 shooting stars and ordinary meteors this is the case, and hence 

 the Meteor Spectroscope requires no slit. Observers furnished 

 with the new instrument will direct it like an opera-glass to 

 the part of the sky most favourable for the observation of the 

 November shower, and as a shooting star makes a line of light 

 in the sky, it will give one or more lines of light in the spec- 

 troscope. If, for example, we had a sodium meteor, it would 

 give a yellow line in the sky, and a yellow line, occupying the 

 sodium line place, in the spectroscope. If silver were present 

 together with sodium, the meteor train would have a greenish 

 tinge, and three lines would appear in the spectroscope — 

 yellow, green, and blue. 



Those who intend to take part in these highly curious in- 

 quiries should provide themselves in time with Meteor Spec- 

 troscopes, and should, with the help of an ordinary spectro- 

 scope, study in advance the spectra of the metals and other 

 substances most likely to be seen when the meteors are in the 

 field. 



The study of meteors is already highly indebted to Mr. 

 Alexander Herschel, whose labours are recognized as of the 

 highest value by every physicist of eminence ; and we have no 

 doubt that his " Meteor Spectroscope ;; will contribute effi- 

 ciently to the progress of our knowledge of shooting stars. 

 To Mr. Browning belongs the credit of carrying Mr. Herschel' s 

 plans most successfully into operation, by the construction of 

 prisms with an accuracy of angle and surface extremely difficult 

 to obtain. 



Mr. Alexander Herschel recently gave a lecture at the 

 Royal Institution, "On the Shooting Stars of the year 1865 — 66, 

 and on the Probability of the Cosmical Theory of their 

 Origin." He commenced by adverting to the probability 

 established by Professor Newton, of Yale College, U.S., " that 

 in the current year, 1866, a prodigious flight of meteors, the 

 most imposing of its kind, and visible over a large area of the 



