Relationships between Stacking Velocities and Root Mean Square Velocities

We saw in chapter 4 (Formula 4.23) that for a subsurface consisting of homogeneous horizontal layers, the time for the signal to travel from source to reflection point and then to geophone, T_x, and the distance between source and geophone, X, are connected by the equation: 7.1$$T_X^2 = {C_1} + {C_2}{X^2} + {C_3}{X^4} + \cdot \cdot \cdot + {C_j}{X^{2j - 2}} + \cdot \cdot \cdot $$ in which $${C_1} = T_o^2$$ (T_o = time for two way vertical travel.) and $$ {C_2} = {1 \mathord{\left/{\vphantom {1 {v_{RMS}^2}}} \right.\kern-\nulldelimiterspace} {v_{RMS}^2}}$$ .