SOME UNSOLVED SCIENTIFIC PROBLEMS 



The controversy as to solar time thus raised proved 

 one of the most curious and interesting scientific dispu- 

 tations of the century. The scene soon shifted from 

 the sun to the earth ; for a little reflection made it clear 

 that the data regarding the sun alone were not suffi- 

 ciently definite. Thus Dr. Croll contended that if the 

 parent bodies of the sun had chanced to be "flying 

 stars" before collision, a vastly greater supply of heat 

 would have been engendered than if the matter merely 

 fell together. Again, it could not be overlooked that a 

 host of meteors are falling into the sun, and that this 

 source of energy, though not in itself sufficient to ac- 

 count for all the heat in question, might be sufficient to 

 vitiate utterly any exact calculations. Yet again, Pro- 

 fessor Lockyer called attention to another source of 

 variation, in the fact that the chemical combination 

 of elements hitherto existing separately must produce 

 large quantities of heat, it being even suggested that 

 this source alone might possibly account for all the 

 present output. On the whole, then, it became clear 

 that the contraction theory of the sun's heat must it- 

 self await the demonstration of observed shrinkage of 

 the solar disk, as viewed by future generations of ob- 

 servers, before taking rank as an incontestable theory, 

 and that computations as to time based solely on this 

 hypothesis must in the mean time be viewed askance. 



But the time controversy having taken root, new 

 methods were naturally found for testing it. The ge- 

 ologists sought to estimate the period of time that must 

 have been required for the deposit of the sedimentary 

 rocks now observed to make up the outer crust of the 

 earth. The amount of sediment carried through the 



VOL. IV. 14 2O9 



