MODERN SCIENCE. 213 



Schiaparelli has identified the orbits of five meteoritic 

 swarms with the orbits of various known comets. Besides 

 the swarms, there are sporadic (chance) meteorites strewed 

 throughout our system, and so numerous are they that no 

 less than TWENTY MILLIONS enter our atmosphere DAILY 

 according to Prof. Newton, and if all were seen their 

 number would probably exceed one hundred millions; so 

 that "our solar system is a meteoric plenum in which 

 sporadic meteorites and swarms of greater or less density 

 are moving in orbits more or less elongated around the 

 sun." There seems also to be conclusive evidence that 

 they are strewed throughout universal space, and not 

 throughout our system only. This question has been worked 

 out by Norman Lockyer very elaborately, and in his book 

 he has co-ordinated all that is known at present about 

 nebulae, comets, and meteorites. 



1836 . Norman Lockyer, besides co-ordinating 

 the labours of other astronomers, physicists, and his own, 

 has contributed important astronomical and SPECTROSCOPIC 

 OBSERVATIONS on meteorites. He has all but proved their 

 ubiquitous presence in countless swarms or streams through- 

 out space as we just mentioned ; he has just pointed out 

 the importance of the part they may play: (i) as factors 

 modifying comets, gravity, light, heat, electricity; (2) as 

 possible and probable elements contributing to the preser- 

 vation of solar energy,* and even the formation of nebulas 

 and stars; (3) as agents causing the phenomena of variable 

 stars, and Novae. With regard to the last mentioned 

 phenomena, he has, upon apparently conclusive evidence 

 spectroscopic in the main supplemented the information 

 given us by W. Herschel and KirchhofT, by the important 

 fact that the intermittent increase of luminosity presented 

 by many of these variable bodies, and not by them alone, 

 but by comets besides, is due to their colliding with meteoric 



* This view is confidently opposed by Helmholtz and Sir William 

 Thomson (now Lord Kelvin), who ascribe the sun's energy to shrinkage 

 by gravity. Lord Kelvin points out that the energy which may be 

 derived from meteoritic impact is insignificant by the side of that derived 

 from shrinkage. 



