506 PROCEEDINGS OF THE AMERICAN ACADEMY. 



Special Symbols (non-vectorial). 



a, /3, singular lines (§ 9). 



7, spacial lines; 5, temporal lines (§ 9, 37). 



«, electric charge (§ 48). 



M, material density (§ 4.5); Mq, density under no relative motion. 



p, electric density (§ 54) ; p^, density under no relative motion. 



v?, electric scalar potential (§ 48). 



m, mass; Wo, mass under no relative motion. 



/, time (also Xa). 



u, V, velocities. 



.r, y, z, space coordinates (also Xi, Xi, Xz). 



I, idemfactor. 



L, Lagrangian function (§ 56). 



R, a perpendicular interval (§ 43). 

 Special Symbols (vectorial). 



a, (three-dimensional) ordinary vector potential (§ 48). 



b, a special four-dimensional "radiation field" (§ 53). 

 C, extended curvature (§ 22, 35). 



e, (three-dimensional) electric force (§ 49, 50). 



f, (three-dimensional) mechanical force (§ 35). 



g, as in dg, special vector of extended momentum (§ 47). 

 h, (three-dimensional) magnetic force (§ 49, 50). 



1, extended light-vector, singular ray (§ 43). 



m, extended (four-dimensional) vector potential (§ 48, 55). 



n, unit normal to (6)-curve (§ 43). 



p, geometric potential vector (§ 43). 



q, vector of extended electric current density (§ 54). 



r, four-dimensional radius vector. 



S, as in f/s, vector element of arc. 



V, (three-dimensional) velocity (§ 43). 



w, unit tangent to (a)-curve. 



E, electric 2-vector (§49). 



H, magnetic 2-vector (§ 49). 



M, electromagnetic 2-vector (§ 48). 



P, geometric 2-vector field (§ 43). 



S, as in dS, element of (two-dimensional) surface. 



S, as in dS, element of three-dimensional volume. 



s, as in ds, element of four-dimensional volume. 



