Résumé : The CHARM II Collaboration has built a massive, fine-grained calorimeter for the study of the elastic scattering upsilon // mu e **(** minus **) yields upsilon // mu e **(** minus **). A short description of the detector will be followed by the presentation of some results obtained by exposing 40 of the 441 planes of the calorimeter to a beam of electrons and pions. Comments will be given about the conditioning procedure followed for the 154,560 limited streamer tubes which compose the active part of the calorimeter.