172 Prof. D. Kirkwood on the Nebular Hypothesis. 
the third, equal toasemi-cireumference. At the same time, : 
gave rise to a periodic inequality, which depends on the smal 
all the care Delambre took in his observations, he could not re 
cognize this inequality, which, while it evinces its extreme small- 
ness, also indicates, with a high degree of probability, the exist 
ence of a cause which makes it disappear. In our hypothes!® 
* Dr. Nichol. : 
5 
