On the Variation of the Moon’s Motion. . 389 
perigonii penitus tubo adnatus, margine 4—5-crenatus. Stamina 
4-5, e sinubus disci, lobis perigonii opposita: filamenta brevia, 
subulata: anthere biloculares; loculis fasciculo filarum araneo- 
sarum ad basim lobi perigonii annexis. F'@m. ignota. Fructus 
ies stylo unico superatus, unilocularis, monosspermus. 
Frutex in Georgia et Carolina Superiore vigens, glaber, cortice 
griseo. Folia opposita, uncialia, membranacea, ovalia, margine 
integerrima subundulata, breviter petiolata, venosa, subtus palli- 
diora. Pedunculi axillares, solitarii, folio breviores, ebracteolati, 
umbellam 3-8-floram gerentes; floribus . parvis virescentibus, 
intus flavidis. 
Sp. Darsya UMBELLULATA.—Hab. Near Milledgeville, Geor- 
gia, Dr. Boykin, and at Macon, Prof. Darby: also at Lincoln- 
ton, North Carolina, Mr. M. A. Curtis. 
I intended here to record some observations made last season 
upon the ovula and fecundation of Comandra, which, although 
exhibiting the same general plan as in Thesium, according to the 
investigations of Decaisne, appear to differ considerably in some 
particulars. But as the season approaches when I may be able to 
repeat and extend the examinations, these remarks are for the 
present deferred. “ 
= 
Arr. VII.—Variation, or the alternate Acceleration and Retard- 
ation of the Moon in the different quadrants of its orbit ; by 
~ James H. Corry. 
, 
In the year 1590 Tycho Brahe, a Danish nobleman and a zeal- 
ous astronomical observer, discovered the fact that the moon 
moves faster when it is new or full than at other times, and slow- 
est when it is midway between these points, or in quadrature, 
and consequently that it is alternately accelerated and retarded in 
alternate quadrants of its orbit. This inequality we denominate 
variation. The cause of it was not known till the discovery of 
the principle of universal gravitation by Sir L Newton, when it 
was shown to be a necessary consequence of the sun’s attraction. 
In an article on the secular acceleration of the moon’s mean 
motion, published in the Journal of Science and Arts for October, 
1844, it was shown that if we take the quantity of matter in the 
earth as the unit by which to measure other quantities of matter, 
Seconp Serizs, Vol. I, No. 3.—May, 1846. 
