1879.] on (he Sfonj of the Novcvihcr Mrfrors. 45 



Earth, Venus, aud Jupiter. Accordingly, if anyone could be found 

 able to calculate liow niucli etlcct would be produced in eacli of tlie 

 five cases, the calculated amount of shifting of tlic orbit could be 

 compared with the observed amount, which is 29' in 3oi years, and 

 this would at once tell which of the five possible orbits is the true 

 one. 



These iiapers of Professor Newton's were published in 18G4. 

 Before the computations which he had indicated could bo attempted, 

 it was necessary that the direction in which the meteors enter the 

 earth's atmosphere should be known much more accurately than it 

 then was, in order to enable astronomers to comjiute the exact forms 

 and positions of the five possible orbits. This observation then was of 

 the greatest importance in 1866, and it was on this account that all 

 the astronomers on that occasion devoted nearly all their efforts to 

 determining with the utmost precision the exact point of the constel- 

 lation Leo from which the meteors seemed to radiate. This important 

 direction was ascertained during the great meteoric shower on the 

 morning of the 14th of November, 1866, and immediately after 

 Professor Adams and his two assistants in the Cambridge Observatory 

 set to work at their arduous task. This great calculation required 

 the solution of a problem in mechanics which had never before been 

 attempted, and involved an immense amount of tedious labour. 

 Amidst all these difficulties Professor Adams triumphed ; and after 

 months of toil he was able to announce in the following March that if 

 the meteors are moving in the large orbit, Jupiter would produce a 

 shifting of the orbit in each revolution amounting to 20', the attrac- 

 tion of Saturn would add to this 7', Uranus would add 1' ; the effect 

 of the earth and the other planets would be insensible. Adding these 

 numbers together, the whole effect, according to Mr. Adams's compu- 

 tation, is 28', almost exactly the same as the observed amount which 

 had been determined by Professor Newton, which was 29'. But if the 

 meteors were in any of the other four possible orbits, the total amount 

 would never exceed 12'. Here, then, we have reached the final result : 

 the long orbit is the orbit of the meteors. This great discovery was 

 published in March, 1867. 



PROFESSOR SCHIAPPARELLI. 



Meanwhile Signer Schiapparelli, of Milan, was labouring in 

 another direction. It was evident from the observations that the 

 meteors were drawn out into a long stream. What was the cause of 

 this ? Signer Schiapparelli pointed out that if a cloud of meteors 

 were started under conditions which were not quite the same, each 

 meteor would pursue its own orbit, which would differ from the 

 others. If they were treated almost exactly, although not quite, alike 

 at starting, their various orbits would lie excessively close to one 

 another, and would be undistinguishable in most respects. But if 

 there be any effect which goes on accumulating from revolution to 



