PROGRESS OF MODERN ASTRONOMY 



is all-powerful, he forces them to describe orbits either 

 elliptical or hyperbolic, their paths being equally pos- 

 sible in all directions, and at all inclinations of the 

 ecliptic, conformably to what has been observed. Thus 

 the condensation of nebulous matter, by which we 

 have at first explained the motions of the rotation and 

 revolution of the planets and their satellites in the same 

 direction, and in nearly approximate planes, explains 

 also why the movements of the comets escape this 

 general law." 8 



The nebular hypothesis thus given detailed comple- 

 tion by Laplace is a worthy complement of the grand 

 cosmologic scheme of Herschel. Whether true or false, 

 the two conceptions stand as the final contributions of 

 the eighteenth century to the history of man's ceaseless 

 efforts to solve the mysteries of cosmic origin and cos- 

 mic structure. The world listened eagerly and without 

 prejudice to the new doctrines; and that attitude tells 

 of a marvellous intellectual growth of our race. Mark 

 the transition. In the year 1600, Bruno was burned 

 at the stake for teaching that our earth is not the cen- 

 f the universe. In 1700, Newton was pronounced 

 "impious and heretical" by a large school of philoso- 

 phers for declaring that the force which holds the plan- 

 ets in their orbits is universal gravitation. In 1800, 

 Laplace and Herschel are honored for teaching that 

 gravitation built up the system which it still controls; 

 that our universe is but a minor nebula, our sun but 

 a minor star, our earth a mere atom of matter, <>ur 

 race only one of myriad races peopling an infinity 

 of worlds. Doctrines which but the span of two hu- 

 TOL. in 4 39 



