6 ANNUAL RECORD OF SCIENCE AND INDUSTRY. 



NOVEL RELATIONS AMONG THE PLANETS. 



At the recent meeting of the National Academy of Science, 

 at Washington, a most eloquent and elaborate essay was read 

 by Professor Stephen Alexander, the astronomer, of Prince- 

 ton, New Jersey. Some twenty years ago Professor Alex- 

 ander communicated to the scientific world an original class- 

 ification of the nebulae, in w^hich, among other things, but by 

 a different process of reasoning, he anticipated the recent 

 conclusion of Proctor that our Milky Way is a spiral nebula. 

 Since then Professor Alexander has been busily engaged on 

 the plans and the erection of the magnificent observatory at 

 Princeton, which the college owes to the munificence and sci- 

 entific interest of General Halsted. Notwithstanding the 

 heavy duties imposed upon him as a teacher. Professor Alex- 

 ander, who is now the oldest of living American astronomers, 

 has found time to engage in the laborious numerical compu- 

 tations incident to one of the most difficult problems that of- 

 fer themselves to the consideration of astronomers, while at 

 the same time it is by far the grandest. This is nothing less 

 than the discovery of those laws which governed the original 

 formation of the universe, and especially of our planetary 

 system. To this investigation Kepler gave many years of 

 patient toil, and though he honestly threw away as too arti- 

 ficial the many curious laws that he at one time thought he 

 had discovered, yet there remained the so-called "Three Laws 

 of Kepler " to challenge a Newton to find out their hidden 

 meaning, and to reveal to him the truth of the law of gravi- 

 tation. Next Bode found the famous relation between the 

 radii of the planetary orbits, which contributed so much to 

 the discovery of the planet Neptune, and of the group of as- 

 teroids between Mars and Jupiter. Since Bode's day. Kirk- 

 wood and Chase have worked with some success upon the 

 planetary harmonics ; but, outstripping both in the exactness 

 of his results, comes the veteran Alexander. It would be im- 

 possible here to give even a small portion of the innumerable 

 remarkable coincidences and verifications that have been re- 

 vealed to the professor we say "revealed" advisedly, al- 

 though it is evident that he has pursued a strictly logical, 

 and in many cases a purely inductive, method in the dis- 

 covery of the wonderful ratios that he has shown to exist not 



