Tlie Theory of Temporary Stars. 



13- 



second column by 7, and in the fifth those obtained on dividing 

 the numbers in the fourth column by 8.^ 



Table III. 



The agreement between the third and fifth columns of Table 

 III. is very striking," and fully warrants us in assuming that the 

 rate of expansion at all parts is pretty much the same. The 

 difficulty lies in the interpretation of this fact, not in its estab- 

 lishment. 



Kapteyn^ and Wilson^ have independently arrived at the 

 conclusion that what we see is not a motion of the nebulous 

 matter, but the light of the outburst reflected successively from 

 more and more distant pkrts of a pre-existing nebula ; Wilson 

 has computed the distance of the Nova on this assumption, and 

 finds it to be about 250 light-yeai's. The hypothesis accounts 

 very well for the agreement between the rates of expansion at 

 diflferent points, and obviates the ascription of enormous 

 velocities to masses of matter ; nevertheless it appears to me 

 that there are serious difficulties in the way of its acceptance. 



In the first place, the apparent rate of expansion was too slow 

 to be consistent with it ; the time interval from 23rd Feb. to 

 13th Nov. is 263 days, that from 23rd Feb. to 20th Sept. is 209 



1 Ritchey's method of measuring these distances on enlarged photographs, by means of 

 a scale, is obviously better suited to the determination of ratios than of differences ; hence 

 the method of comparison adopted above, which uses the actual measurements, atid 

 neglects the differences tabulated by liitchey. 



- The onlj' discrepancy of any real importance is that furnished by condensation /. 



3 Astr. Nach., No. 3756. 



4 Nature, 2nd Jan., 1902. 



