MIRACLES OF SCIENCE 



is not a uniformly gaseous mass. There is filmy, ten- 

 uous matter permeating its structure, but its main 

 substance seems to be composed of more or less dis- 

 crete nodules or nuclei. 



THE SPIRAL NEBULA AS MOTHER OF WORLDS 



Professor Keeler himself noted this discrepancy, 

 but it remained for Professor T. C. Chamberlin, of 

 the University of Chicago, and his younger colleague, 

 Professor T. R. Moulton, to take the matter up, and 

 to develop a new theory of world-making based on 

 observation of the spiral nebula, but harmonized with 

 all the new facts of astronomy and geology that had 

 come to contradict the old hypothesis. 



The new theory assumes that, the typical spiral 

 nebula, as revealed to us by the telescope, is in point 

 of fact the parent structure of a solar system such as 

 ours. Stated otherwise, it assumes that our solar sys- 

 tem was once a spiral nebula differing only in size 

 from any one of the hundreds of thousands of such 

 bodies that still tenant the universe. It further as- 

 sumes that the clustered masses to be seen here and 

 there along the arms of the spiral nebula (knots in 

 the skein, Professor Chamberlin has suggestively 

 called them) are nuclei out of which will ultimately 

 develop a group of planets more or less similar to 

 those that constitute the sun's family. 



A spiral nebula then, in this view, is a system of 

 worlds in the making. The central nucleus is the 

 future sun. Various of the spots that lie along the 

 arms of the spiral are the nuclei of future planets. 

 Professor Chamberlin calls nuclei of all sizes "plane- 



8 



