A FAMOUS ASTRONOMICAL PROBLEM 503 



The reader should be cautioned against obtaining the impression 

 that Seeliger's two ellipsoids represent the truth as to the law of 

 distribution of density, for such is not the case. A very large number 

 of ellipsoids, doubtless decreasing rapidly in density as one proceeds 

 from the sun outward, would be required to represent the actual law. 

 Seeliger found that the attractive effect of the mass inside of the 

 ellipsoid with maximum radius 0.24 was essentially independent of the 

 law of distribution; and for convenience in the computations he there- 

 fore assumed the density in the said ellipsoid to be uniform. A solu- 

 tion based upon a greater number of constituent ellipsoids would 

 perhaps be a slight improvement. 



The logic of Seeliger's work rests finally upon the reasonableness 

 of his assumptions and deductions concerning the distribution and 

 density of the zodiacal-light materials; and these are not out of 

 harmony with the meager knowledge of the zodiacal light which we 

 have obtained by direct observation. 



In consequence of Seeliger's results further direct observations of 

 the zodiacal light take on renewed interest. 



