Moon's Rising & Setitgy, & he Elevation of H€ £480s 267 could never be of any great amount, being neglected: it is, however, very see why blue ess accurate of the two valuations of the quantity in guostion should have been selected by the text for it is, if anything, gathey less easy of determination than the other. The other disccordance is one of mul or agitude und importance : the text peaks of the hypothenuke of the inson's mid-day shado (rodhagdan८८daprabad. Royuza), for which the countmentary substituto£ %hnt of the shadow . Cast by the moon at the given morrent of SunBet. The commentator attempts to reconceile the discrepancy by saying that the text means here the moon's shadow ax calculated after the nethod of a non-shadow. or again, that the time of sutu8e8 3, in effect, the middle of the daysince the civil day is reckoned from sunrise to sunrise: but eithor of those explanations can |be reg४:ded १४ satisfactogy {he continentator further rges in support of his understanding of the term, bbot we are expressly taught above ( v. 11) 3bak the calculation of appagete longi!ude (ylePad 2) is ko be made in the process for finding the elevation of the HUon's cusps while, if the hypothenue of blhe nou's mmeridian shadow be the one found, there arises no occasion for making that calculation. 10 secmns clear that, unless the 801ntrntal tor's nderstanding of the trus Reope and method of the whole peox8 lb erneous, Ahe substitution which he makes must necessarily be drritted. This is a point to . which we shall recur later. ! १. 'The number o1 minutes in the longitude of the moon dlinninnished by that of the sun gives, when divided by nine hundred, hler lumins a part (lk) : this. multiplied by the number of digits () of the moon's uisk, and divided by twe[ve, gives the sunle corrected (sphalt}. 'The rules laid down in thi verye, for determining the measure of the illuminate part of the moon, applies only to the time between new moon and full moon, when the roon is less than 180° from the sun when her 8xcess of longitude is more than 180°, the rule is to be applied Rs stated belowin verse 3 As he whole diameter of the noon is illuminated when she is half a revolution from the gun, one half her diameter at a quarter of a revolution's distance, and no part of it at the time of conjunc tion, it is assumed that the illurnimatert portion of her diameter will very as the part of t80° by which she is distants on the sun; and hence that, assuming bhe rIssure of the diameter of her disk to be twelve digits, the number digitles illuminated onaly be found by the following proportion 8B of half a revolutbon, or 10,0, is to twelve digits, ge is the moon's distance hom he Sut in minute®x in the corresponding part of the diameter ilmiः mathed: the substitution, if the first ratio, f 6X * 10,5): , gives the rule s state in the text[Her it wil! ]] A¢ }ave for the
