Bīrūnī, Muḥammad ibn Aḥmad, Alberuni's India (v. 1)

(London :  Kegan Paul, Trench, Trübner & Co.,  1910.)



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Definitionof The natural month is the period of the moon's syno-

the lunar                                                                   ^                                                .

month. dical rcvolution. We call it physical because it de¬
velops in the same way as all natural phenomena,
rising out of a certain beginning like non-existence,
increasing by degrees, and growing, standing still when
the climax is attained, then descending, waning away
and decreasing, till at last they return to the non¬
existence whence they came. In the same manner the
light develops on the body of the moon, since she
appears after the moonless nights as a crescent, then
as a young moon (after the third night), and as full
moon, and thereafter returns through the same stages
to the last night, which is like non-existence, at all
events with reference to human senses. It is well,
known to everybody why the moon continues for some
length of time in the moonless nights, but it is not
equally known, not even to educated people, why she
continues some time as full moon. They must learn
how small the body of the moon is in comparison with
that of the sun, that in consequence the enlightened
portion by far exceeds the dark one, and that this
is one of the causes why the moon must necessarily
appear as full moon for some length of time.

That the moon has certain effects on moist substances,
that they are apparently subject to her influences, that,
for instance, increase and  decrease in ebb and flow

Effects of
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