We describe in this paper an experiment using a cloud chamber in a magnetic field of 6200 gauss to determine the average total cross-section of the direct production of electron pairs in aluminium by high energy electrons generated in cascade showers and having energies larger than 30 Mev. We have found after correcting for the spurious events 8.1 electron tridents, which were produced actually by electrons. This figure corresponds to a mean free path of 672±585 cm. or an average total cross-section of (0.25± 0.22)×10-25cm2, for trident production. In the treatment of data, the elimination of spurious tridents has been appropriately considered. The formulas of the total cross-section derived by Bhabha and by Murota et al have been applied in accordance with our experimental conditions to compute the total cross-section. Finally, comparison between the theoretical and experimental values has been made. Our experiment is in fair agreement with the theory of Murota et al. While not in contradiction with that of Bhabha.