The Positive Sciences of the Ancient Hindus c6.10

c6.10

The molecules of a bell vibrate when the bell is struck. The question is—what is the nature of this vibratory movement? Vâtsyâyana and Udyotakara answer that, when the hand strikes the bell, some of the molecules are displaced (from their stable position—*i.e.* there is *karma* in the molecules), and thus a Sanskâra (here a kinetic Sanskâra, momentum) is generated (संस्कार, कम्पसन्तानसंस्कार—Vâtsyâyana and Vâchaspati), and the molecules swing forward under the action of this Sanskâra until they strike the contiguous molecules of air. This now is a case of mutual impact, which divides the momentum between the colliding masses, and the bell-molecules begin to swing backward, the motion continuing under the action of the diminished Sanskâra until they come in collision again with other air-molecules; and then the process is repeated, and the bell-molecules begin to swing forward and backward until the original energy which is parted with in some measure at each impact becomes so feeble as to be unable to produce any kinetic disturbance (कर्म). Similarly, the air-molecules themselves are set vibrating by means of these impacts, and the transmission of the motion would form the wave of air, which the later Nyâya-Vaiśeṣika expressly posit as the vehicle of the sound-wave. But Udyotakara never conceived vibration *in vacuo*, nor does it appear if he meant to include the second species of Sanskâra (elasticity, Sthitisthâpaka-sanskâra) as converted from its potential state (अतीन्द्रियता) into kinetic energy, and thus contributing to the momentum (*vega*). He uses the generic term Sanskâra, which comprehends elasticity as well as momentum due to impressed force. His commentator, Vâchaspati, does not go into details, and does not analyse the momentum. Later writers, however, expressly state that elasticity (Sthitisthâpaka-sanskâra) is one of the causes of vibration, and that elasticity resides not only in the element of earth, but also in air, water, and *tejas* (*cf.* Viśvanâtha).