Intelligence and Miscellaneous Articles. 389 



Now, the anomalistic revolution of the moon, from apogee to apogee 

 again, is performed in the time 



27d i3h i8«» 32«'3; 

 or from apogee to perigee, in the time 



IS'i 18^^39"^ 16«-1. 



Here we have a real instance, exactly corresponding to the case which, 

 for the sake of explanation, we assumed a short time back, and the 

 results are truly such as were there described. During about 4000 

 half-revolutions of the moon, or 2000 revolutions, the pulling force 

 at apogee is gradually diminishing till it becomes a pushing force, 

 and during about 2000 more revolutions, the pushing force at apogee 

 is gradually diminishing till it becomes again a pulling force ; the 

 opposite changes going on in the force at perigee : and thus, for 

 reasons fully explained before, the moon's orbit is gradually con- 

 tracting during 2000 revolutions, and gradually expanding during 

 2000 revolutions more. And although the change in the size of the 

 orbit is totally insensible in observation (for, according to a rough 

 calculation, the utmost accumulation of change in the major axis of 

 the moon's orbit is only ten feet, sometimes in increase and some- 

 times in decrease), yet the consequent alteration in its periodic time, 

 continued through so many revolutions, is sufficient to cause the 

 irregularity in question. The inequality in longitude, as measured 

 on the moon's orbit, exceeds thirty miles, sometimes in advance, and 

 sometimes in retard. 



For a complete understanding of this matter, it must carefully be 

 borne in mind that the force at the apogee, which has been described 

 as a pushing force through 136 years, is not absolutely a pushing 

 force through every month of that time, but that (in consequence of 

 the motion of the moon's line of apses) if we take any period of nine 

 or ten years, the moon's apogee will in that time have passed through 

 every position with regard to Venus, and therefore, upon the whole, 

 during that period of nine or ten years, the force at apogee will have 

 been a pushing force. In like manner, in another period of 136 

 years, if we take any period of nine or ten years, upon the whole, 

 during that period of nine or ten years, the force at apogee will have 

 been a pulling force. 



The general cause of the inequality depending on the argument 

 8p"— 13^', has been sufficiently stated in one of the last paragraphs 

 of the abstract of M. Hansen's paper. 



LXIII. Intelligence and Miscellaneous Articles. 



ON THE GELATINOUS SUBSTANCES OF VEGETABLES. 



MFREMY, in a memoir read before the Academy of Sciences, 

 • has arrived at the following conclusions : — 

 1st. There exists in vegetables, along with cellulose, a substance 

 which is insoluble in water, alcohol and aether, which the author 



