of Natural Philosophy. 149 
should be assigned each to its proper cause; that in lati- 
tude to the obliquity of the axis to the plane of the orbit, 
and that in longitude to the excentric form of the orbit,— 
instead of blending the explanations of both under the 
loose proposition, * the librations of the moon may be ex- 
plained on the: supposition that the moon has a revolution 
on its axis.” In prop. 81, the equality of the times of ro- 
tation and revolution is inferred from the hibrations ; while it” 
is in fact a matter of direct observation, oe must be soe ‘ 
supposed in explaining the librations themselves, In 
82, the elliptical form of the moon’s orbit is inferred froti 
the libration in longitude. ~We very much doubt whether 
the species of oval to which the ‘moon’s orbit most near| 
approaches could have been d from direct <o 
servations on’ so trifling a change of — The proper 
: this part of the subject would be, to — 
infer the elliptical form of the orbit from the abaelved: role 
tion between the anomaly and the apparent diameter; and 
then to employ this conclusion for the explanation of the 
libration i oe longitude 
rop. 83. Schol. In stating the results of Dr. Hers- 
chel’s observations on the altitude of the lunar mountains, it 
is mentioned that “ one was found to be about a mile i 
height; but none of the others which he measured —_ 
os be more than half that altitude. *” By consulting the orig- 
memoir in the Philos. Trans. cotamalibad which hi 
eer published since, it will be seen that Dr. Herschel’s re- 
sults differ much less from the estimates of the older As- 
tronomers, and from the recent and accurate measurements 
of Sehroter, than is here represented. Dr. H. pate 
several over a eee: and one, nearly two miles i in height. — 
Prop. 106. “If recuclesdeigaartoets new, isin coe nneite 
—_— the eclipse of the sun will be central. _ It should be, 
inhabitants of aes part of the earth it will be 
cette aad in the zenith.” | To those parts _of the 
earth at which the moon is never vertical, a 
can happen’ only road ah moon is 08, Att its one, at ‘the : 
the — of conjuncti 
p- 113, which ree: a notion in antecedentia,” 
of the y atelligee BE the superior planets ! from 
one elongation to the next feeder the their. inferior conjunc- 
tion, is no less erroneous than the propositions of former 
