THE METEORITIC HYPOTHESIS. 345 



Prof. Lockyer made a number of careful experiments on the 

 spectra of fragments of "undoubted meteorites/' obtained from 

 the British Museum. These were examined at various tempera- 

 tures, varying from that of the " Bunsen burner " to that of the 

 electric spark with Leyden jar. He finds that, at the lowest tem- 

 perature, the most prominent line of magnesium is a fluting near 

 the wave-length 500. I may here explain that by the term " flut- 

 ing" is meant a series of bright lines, usually three, which are 

 sharp on the side toward the red end of the spectrum, but have a 

 hazy fringe on the blue side. These "fringes," when examined 

 with a powerful spectroscope, are seen to be composed of a num- 

 ber of fine lines very close together. In the case of " iron " meteor- 

 ites, the lines of manganese are the first to make their appearance, 

 owing to its volatility being greater than that of iron. 



Lockyer finds that only the lowest temperature lines of mag- 

 nesium, sodium, iron, chromium, manganese, strontium, calcium, 

 barium, potassium, bismuth,- and nickel are seen in the spectra of 

 the meteorites. 



He shows the probable identity of origin of luminous meteors 

 and falling stars with meteorites, and also that comets are prob- 

 ably composed of meteoric stones. Discussing the observations of 

 the aurora, he attempts to prove that the phenomenon is due to 

 meteoric dust in the " higher reaches " of our atmosphere, and that 

 the characteristic line seen in the auroral spectrum is identical 

 with the brightest fluting of manganese. Dr. Huggins's researches, 

 however, show that this coincidence does not exist ; and some re- 

 cent experiments made by Messrs. Liveing and Dewar with an 

 electric discharge passing through dust show that the dust does 

 not act like a gas, and does not become luminous like the aurora, 

 but that, on the contrary, the electric current drives it out of its 

 path. 



Lockyer next proceeds to discuss the appearances presented by 

 comets,- and the character of the spectra they show at different 

 distances from the sun, and concludes that their spectra very much 

 resemble the spectra of meteorites seen under similar conditions 

 of temperature. He considers that the light of comets is chiefly 

 due to collisions between the component meteorites, and that the 

 observed transparency of comets may be explained by supposing 

 the meteorites to be small, and separated by considerable intervals. 

 A portion of the light of comets, he thinks, may be produced by 

 collisions between the cometic swarm and other swarms existing 

 in space ; and the recorded sudden increase of light in the Pons- 

 Brooks comet of 1883, and the Sawerthal comet of 1888, seems cer- 

 tainly in favor of this idea. 



Lockyer holds the view that both shooting-stars and comets 

 did not originate within the solar system, but are of cosmical ori- 



