The Positive Sciences of the Ancient Hindus c5.s3.t3.1

c5.s3.t3.1

Any number of motions or Vegas may be impressed on a particle, but so long as these are in a uniform direction (नियतदिग्विदिष्ट) the resultant motion or Vega is in a straight line, and may be conceived as one (द्वितीयकल्पना-वैय्यर्थम्, Praśastapâda, कर्मग्रन्थ). It is only when we come to Gamana (curvilinear motion) and its causes that the question of composition assumes a real significance. In all such cases, each separate particle has only one Vega (impressed motion) in a definite direction (नियतदिगाभिमुख्य) at any given instant, but the composition of the successive motions and Vegas in the same particle produces the curvilinear motion (गमन), *e.g.* the rotation of each constituent particle of the potter's wheel. The motion of the body (अवयवी, *e.g.* the wheel) results from the combined motions of the particles (अवयवाः). If pressure or impact produces motion in an opposite direction to the Vega already impressed on the body, the original direction would be changed, as is seen in the case of rebounding (उत्पतन) after impact (अभिघात). The mortar rebounding after striking the pestle is a typical instance of such change of direction in Vega or motion. The impressed force, *e.g.* impact (अभिघात), produces a changed motion in a different direction. One view is that the original Vega (momentum) is destroyed before a new motion and a new Vega are produced by the impact. Others hold that the impact does not destroy the original Vega (momentum), but conjointly with it produces the changed motion and, through such motion, a changed Vega in a new direction. (उलूखलमुसलयोरभिघाताख्यः संयोगो-मुसलगमवेगमपेक्षमाणः मुसले उत्पतनकर्म करोति यद्यपि प्राक्तनसंस्कारो विनष्टः तथापि मुसलोलूखलयोः संयोगः पटुकर्मोत्पादकः तस्य संस्कारारम्भ-साचिव्यसमर्थो भवति अथवा प्राक्तन एव पटु संस्कारः अभिघातान् अविनश्यन् अवस्थित इति *et seq.*, Prasastapâda, कर्मग्रन्थ ।)