214 PROGRESS OF SCIENCE. 



swarms. These swarms, by the impact, break out into 

 sudden incandescence, and add it to the normal light shed 

 before the collision by the stars and comets. It is, on a 

 large scale, the same phenomenon as that which we witness 

 on our earth when meteorites meet our atmosphere : they 

 are ignited, and become, therefore, intensely luminous. Be 

 this as it may, for the point is not altogether admitted by 

 all astronomers yet, Norman Lockyer, upon what appears 

 to him satisfactory evidence, has broached a new theory 

 of the universe, partially guessed by Waterston, viz., the 

 METEORITIC HYPOTHESIS, as distinguished from the Nebular 

 Hypothesis Lockyer's theory being that meteorites are 

 the material out of which worlds are formed. The two 

 theories are by no means exclusive of each other they 

 are easily reconcilable on the contrary, if it be allowed 

 that the two processes actually occur in succession, the 

 meteoritic phase coming after the nebular (gaseous) phase, 

 as an effect of radiation as an effect, that is, of cool- 

 ing, contraction, and chemical precipitation the meteoritic 

 phase in its turn producing the three series of phenomena 

 just mentioned. Norman Lockyer, besides the work just 

 described, and which by the way is the most recent, has 

 enriched science in several departments by numerous 

 investigations and discoveries. He is a master in spectral 

 analysis and solar physics. He had a great share in the 

 elucidation of the constitution of the sun as sketched out 

 in the paragraph referring to W. Herschel. The name 

 of CHROMOSPHERE is due to him, together with our 

 better knowledge of this portion of the sun. A fine 

 example of the excellence of his work we may cite in 

 Mr. Jevons's words : " Wanting some guide as to what 

 more elements to look for in the sun's photosphere, he 

 prepared a classification of the (chemical) elements ac- 

 cording as they had or had not been traced in the sun, 

 together with a detailed statement of the chief characters 

 of each element. He was then able to observe that 

 the elements found in the sun were mostly those forming 

 stable compounds with oxygen. He then inferred that 

 other elements forming stable oxides would probably exist 



