The spectral calculations of the Row which develops near a heated vertical wall in a fluid stably stratified by a salinity gradient are carried out. The case of weak stratification and heating due to a constant heat flux is considered. The numerical results ale compared to the experimental ones. Both on qualitative and quantitative arguments, a satisfactory agreement is obtained. The cell formation process is discussed by focusing on the occurrence of counter-rotative cells and on the instability phenomenon of the simultaneous creation of cells. The high sensitivity of such phenomena to slight disturbances at the initial time is pointed out.