line 8 was the last line created by the agreement of 30 march 1898, and consists of a route between opéra and porte d'auteuil via grenelle. in march 1910, the line was branched off and opened with line 7, and a branch leaving the station of "grenelle" to the port of sèvres (today "balard") was added to the route. the trains alternately traveled along the two branches.