196 Dr. Debus on the Action of Nitric Acid on Glycerine. 



3. The variable part will give rise to a diurnal inequality, 

 having one niaximum and one minimum in the day, and subject 

 to the condition 



The third of these laws does not hold, with respect either to 

 the solar- or to the lunar-diurnal variation. Thus, in the solar- 

 diurnal variation of the declination, the changes of position of 

 the magnet throughout the night are comparatively small, and 

 do not correspond, with change of sign only (as requii-ed by the 

 foregoing law), to those which take place at the homonymous 

 hours of the day. The phsenomena of the lunar-diurnal varia- 

 tion are even more opposed to the foregoing law, the variation 

 having two maxima and two minima of nearly equal magnitude 

 in the twenty-four lunar hours, and its values at homonymous 

 hours having for the most part the same sign. Hence the phse- 

 nomena of the diurnal variation are not caused by the direct 

 magnetic action of the sun and moon. 



It is true that if we proceed another step in the approximation, 

 and include in the values of the disturbing forces the terms con- 



b c 

 taining the first powers of -, -, the formerwill produce in the re- 

 sulting values of AS, AU,and AV, terms containing sin 26, cos2^, 

 and giving rise therefore to a semidiurnal inequality. But the 



3;' 

 coefficient ^, by which these terms are multiplied, amounts in 



the case of the sun only to -^-q-qq, while in that of the moon it is 

 about y'^; and the magnitude of the semidiurnal inequality 

 should bear to that of the diurnal the ratios designated by these 

 small fractions. The facts are altogether opposed to this result. 

 The coefficient of the solar diurnal inequality of the declination 

 at Dublin, in the mean of the entire year, is 3''52, while that 

 of the semidiurnal is 2'" 13, — nearly two-thirds of the former. 

 In the case of the lunar-diurnal variation, the semidiurnal in- 

 equality is greater than the diurnal. 



XXVI. On the Action of Nitric Acid on Glycerine. — First 

 Memoir. By Dr. H. Debus*. ' 



THE constitution of glycerine may be considered, according 

 to the excellent investigations of Berthelot, Luca and 

 Wurtz, to be analogous to that of alcohol. If the atomic group 

 Q3 jj[5^ replaces three atoms of hydrogen in thi'ee atoms of 

 water, a formula is obtained which expresses the composition of 



* Communicated by the Author. 

 t C=12, 11=1, 0=16. 



