सिद्धान्तशिरोमणि: गणिताध्याय (भास्कराचार्य - ग्रहगणित, मध्यमाधिकार व स्पष्टाधिकार सटीक)

26 during that month. The next lunar month is termed as the Nija-māsa or the month which is the true. In this convention however, there may occur two Saṁkrāntis in one particular lunar month. For this to happen two cri- teria are to be satisfied namely that, that particular lunar month must be greater than the concurrent solar month and secondly one of the two Saṁkrāntis must occur imme- diately after a New-moon so as to permit the second Saṁk- rānti to occur just before the lapse of the lunar month. The Sun coming to his perigee roughly about the lunar month Mārgasira, and as such having the quickest motion at that point, he covers the length of the Rasi of 30° within the shortest span of time making that Solar month shorter than the corresponding lunar month. Since the months Kārtica and pausha, one before and the other after Mārga- sira, also being thus longer than the corresponding solar months, two Sankrāntis could occur, if at all, in these three lunar months. If they occur, that lunar month is termed a Kshayamāsa. Since two lunar months are to correspond to two Saṁkrāntis, convention has it that two lunar months lapse simultaneously during that lunation, the previous lunation running during the forenoon and the subsequent lunation during the afternoon. Thus a Kshaya māsa is also called a yugalībhūta māsa or a twin māsa, which therefore makes one lunation virtually vanish. On account of this vanishing’, it is called a Kshayamāsa. After what an inter- val of time this Kshaya māsa occurs how a month precedes it having no Saṁkrānti and how again a lunation follows it without a Saṁkrānti will be seen in a subsequent context. This convention pertaining to the institution of an Adhikamāsa goes by the name ‘Inter-calation’. It was mentioned before that on an average an Adhikamāsa occurs once in 32½ solar months roughly–Also, Adhikamāsas are the excess of lunations over the solar months in a given period. There being 51840000000 solar months in a Kalpa and 53433300000 lunations the number of Adhikamāsas is therefore 1593300000 as mentioned,