The Positive Sciences of the Ancient Hindus c6.8

c6.8

But how does the first sound produce the second, the second the third, and so on? At every step the efficient cause, the impact of some vibrating molecule against a contiguous molecule of air, must be posited, and this is equally applicable to a sound produced by a sound (**शब्दजशब्द**) as to one produced by conjunction and disjunction (**संयोगज** or **विभागज**). In other words, the sound-wave (**शब्दसन्तान**) in Âkâśa necessarily implies an air-wave. The Mimâmsaka view, then, that explains the propagation of sound by the transmission of the original oscillatory motion through the successive layers of air by means of successive impacts or pressures producing conjunction and disjunction of air-molecules (वायवीयाः संयोगविभागाः—Śabarabhâṣya), or rarefaction and condensation (प्रचय—Vâkyapadîya), is also implied in the Nyâya-Vaiśeṣika doctrine of the sound-wave (शब्दसन्तान), the difference being that in the latter the air-wave, which is conceived as a mode of serial motion (गति-सन्तान), is only the vehicle or medium of propagation of a so-called sound-wave in Âkâśa, which is not itself a mode of motion. This is what we find expressly and elaborately formulated in the later Nyâya-Vaiśeṣika (*vide* Gangeśa, Chintâmaṇi, *supra*).