वययनतरण — Air-driven Devices: Bellows, Fans and Vanes

Air is the most elusive of Bhoja's four seeds: it cannot be seen, it escapes any open vessel, and it moves only when pressed or released. Chapter 31 of the Samarāṅgaṇasūtradhāra nevertheless gives air a full set of verses. It explains how air is captured and driven (31.31–32), how it becomes the seed of water-machines when it is "taken in, given, filled and pushed back" (31.35), what parts an air-machine needs (31.38–41), and what air machines can do: make wooden birds sing through a copper tube (31.89–90), make figures dance, sing and play flutes "by air held and released" (31.77–78), and produce the sound of every musical instrument (31.55–57, 31.94). This article collects these passages and reads them in modern terms. The key operations are those of pneumatics: generating a flow (bellows, fans), storing it (sealed bags), and controlling it by alternately blocking and releasing it (niruddha-mukta), which is the function of a valve. The sounding devices correspond to whistles and reed or edge-tone pipes. The article compares Bhoja's statements with the singing birds of Hero of Alexandria and the automatic instruments of the Banū Mūsā, and marks the readings that remain uncertain. Article 5 of the series Yantravidhāna Studies (SSD-31), on chapter 31 of Bhoja's Samarāṅgaṇasūtradhāra. Verses discussed: 31.31–41, 31.77–78, 31.89–94. Web version: sanskritmanthan.in/a/ssd-31-05-vayu-yantra