History of Chemistry in Ancient and Medieval India, Incorporating the History of Hindu Chemistry by Acharya Prafulla Chandra Ray c40.s5.11

c40.s5.11

The wave-motion and current-motion or convection have been termed *gati-santana* (*gati* means velocity, *santana* denotes serial motion; motion which progresses forwards). Mere vibration has been described as *kampa-santana* or *spandana*. Charaka notes three kinds of *santanas*, serial motions, viz., those of water, sound and light. Chakrapani points out that a wave of sound travels more rapidly than a wave of water, and much less rapidly than a ray of light. The last named implies the rectilinear propagation of indefinitely minute corpuscles, in all directions, with inconceivable velocity, and a sort of conical dispersion (*cf.* Uddyotakara—Vachaspati). A wave of water implies the transmission of vibratory motion in the water particles A wave of sound is conceived by some on the analogy of a wave of water; only the air waves, or the sound waves in and through the vehicle of air waves, travel by concentric circles, not in one but in all planes (this assumes transverse waves). Others hold that the air waves, or the sound and air waves, are propagated by the transmission of the vibration in all directions, leading to conjunction and disjunction of air particles, so that the waves may be said to expand by alternate concentric spherical layers of rarefaction and condensation (this assumes longitudinal waves). The Vakya-padiya describes articulate sounds (*varnas*), and indeed all sounds (*sabdas*), as only forms of air set in motion, with rarefaction and condensation, and capable of variations of velocity and configuration (Vakya-padiya, Kanda I, Sloka 109).