July 5, 1901.] 



SCIENCE. 



complexity of the resulting expressions 

 who has not himself looked into the prob- 

 lem. Delaunay, at one time director of 

 the Paris Observatory, carried this investi- 

 gation farther than any of his predecessors 

 had done, bat though it had occupied his 

 almost undivided attention for twenty 

 years, it was still unfinished at the time 

 of his death. (He was unfortunately 

 drowned at Cherbourg in 1872 by the cap- 

 sizing of a pleasure boat.) We have in 

 this country to-day three investigators who 

 are perhaps the greatest living authorities 

 on this subject — Professors Newcomb, Hill 

 of New York, and Brown of Haverford. 



The general problem of three bodies has 

 proved a very fascinating one. If, for in- 

 stance, Mars and Jupiter were of approxi- 

 mately the same dimensions as the sun, the 

 determination of their respective motions 

 would be vastly more complex than it now 

 is. Mr. G. H. Darwin has been giving 

 much attention to this class of problems 

 bringing out some interesting results. Al- 

 though the problem does not confront us 

 in this unmanageable form in our own sys- 

 tem it will eventually find practical applica- 

 tion in unraveling the intricacies of the 

 stellar motions. 



Probably no achievement in the domain 

 of science ever produced so profound an 

 impression upon the unprofessional public 

 as the discovery of Neptune by a purely 

 theoretical investigation undertaken in- 

 dependently by Leverier and Adams, pre- 

 dicting its place in the heavens before it 

 had ever been seen, or at least recognized 

 as a planet. It is unnecessary now to re- 

 hearse the familiar story of that brilliant 

 discovery. It was somewhat like the egg 

 of Columbus, but up to the present time the 

 attempts to apply the process in other re- 

 gions of the planetary system have not been 

 attended with success. The first such at- 

 tempt was by Leverier himself, followed in 

 1859 by his confident announcement of a 



planet between Mercury and the Sun. 

 The prestige of Leverier's name, accom- 

 panied by a supposed view of the planet by 

 Dr. Lescarbault, an amateur astronomer, 

 proved sufficient to carry conviction gen- 

 erally ; and Vulcan found a place with the 

 other planets in many books written thirty 

 or forty years ago. No one else, however, 

 whose authority was worth much claimed 

 to have seen the planet until the occurrence 

 of the total eclipse of the sun July 29, 

 1878. At this time Professor Watson, of 

 Ann Arbor, and Lewis Swift, of Rochester, 

 believed they had each seen one and per- 

 haps two planets near the sun. The rep- 

 utation of both as skilled observers natu- 

 rally gave great weight to their authority, 

 but the planets were never seen again and 

 a critical examination of the places as- 

 signed renders it practically certain that 

 fixed stars were mistaken for planets. Vul- 

 caa as a single large planet within the orbit 

 of Mercury is now by the unanimous ver- 

 dict of the astronomical profession rele- 

 gated to the realm of myths. It was very 

 natural to attempt to apply the process to 

 the discovery of planets beyond Neptune, 

 but although some indications of one and 

 possibly two such have been suspected, 

 nothing of the kind has yet been seen. 



The eighteenth century ended with a list 

 of known planets numbering 7 not including 

 satellites. The nineteenth began with eight, 

 the first day of January, 1801, being distin- 

 guished by the addition to the list of Ceres, 

 the first of the long line of asteroids to be 

 detected. The fortunate discoverer was 

 Gieuseppe Piazzi. The scene of Piazzi's 

 activities was the University of Palermo, 

 where he had been diligently engaged for 

 nine years with the most perfect instrument 

 which the skill of that day could produce 

 in accumulating materials for a great stellar 

 catalogue. At the time of which we are 

 speaking his attention was directed to a 

 place in the constellation Taurus on account 



