890 



from whifli C = 1.635 and H = 0.32 is calculated. The value of 

 H is of the former order of magnitude. But C has decreased to 0.8 

 of its former value. This appears still more clearly when benzene 

 is compared with hexamethjlene or cyclohexane. With this latter 

 substance we have also the cyclic binding of 6 carbon atoms; only 

 the coincidence of two xalencies for carbon has disappeared. The 



T 



formijla is C^Hj, and — =13.9. Hence the comparison with benzene 



gives the two following equations: 



6C'+12H = 13.9 



and 6C+ 6 H = 11.73 



or H = 0.3616 



and = 1.593 



I will still give a few values calculated in the meantime, viz. 



propylbenzene, calculated with benzene and CH2:=2.76, equal to 



Tk 

 20.01, — being equal to 19.772, and chlorobenzene with CI — H :^ 



I'k 

 2.185 calculated at 13.915 and found 14.18. 



But all the nitriles appear to give much too high values of 



Tk 



— , and so for />. and are associating in a high degree. Even benzo - 

 nitril, but this nitril in a less degree than the others. 



Astronomy. — "Investigation of the inequalities of approximately 

 monthly period in the longitude of the moon according to the 

 meridian ohservations at (rree/niuch". Addendum, ^y J. E. 

 DE Vos VAN Steenam-JK. (Communicated by Prof. E. F. v. d. 

 Sande Bakhuyzen). 



Professor Battermann and Prof. Ernkst Brown have both been 

 so kind as to point out to me, in letters to Prof. Bakhuyzkn, that 

 Brown's theoretical value, quoted by me, for the motion of the 

 moon's perigee (p. 140), which was taken froui Monthl. Not. 64 

 532, does not quite agree with his final result, which was published 

 by him in Memoir.^ R. A. -S'. 59, 94 (couip. also Monthl. Not. 70, 

 3). If we use the value assumed by me for the ellipticity of the 

 earth 1 : 297.5, then the theoretical result for the sidereal motion 

 in a Julian year for 1850 becomes 146435''16, so that my result 

 iVom the observations 146435"31 is now only 0"I5 greater, against 

 0"26 formerly. 



