AbstractThe formulas derived by the author in a preliminary paper for taking into consideration refraction when dealing with the problem of a vertical plane are extended to the three‐dimensional case. Vector analysis is extensively applied. Among others it is shown that in the general case the 3 horizontal twodimensional vectors, i.e.1) the gradient of the time of reflection2) the direction of true dip3) the vector from the shot point to the projection of the reflecting point, point into 3 different dir