The experimental and theoretical work was aimed at determining the neutron fission cross sections of U-235 and U-2S8 in the energy range 0.3 - 12.5 MeV with good resolution and reasonable statistics. The main instrument used was the 100 MeV electron linear accelerator of the laboratory, providing a pulsed neutron source in connection with a bremsstrahlung target. To carry out the research, it was primarily necessary, to understand the fission process in detail and the associated models. To describe it and the cross sections required the use of the liquid drop model, shell corrections, the optical and the statistical model. To see the present work in perspective, a review of past and present work in this field was necessary. The main instrument, apart from the accelerator, with which the experiments were carried out, was a high resolution gas scintillator, used as a time-of-flight spectrometer. This scintillator was developed by the author with Xenon as the gas in question, and by using a Cf-252 natural fission source for testing during the development. The monitor detectors, chosen for the experiments, were standard neutron detectors. During a series of accelerator tests the optimum electronic data collection system was developed by the author. This was assisted by a bi-dimension data storage programme for a FDP-7 on line computer, earlier written by J. D. Kellie. Apart from the time to energy conversion, which was done by a computer code by J. D. Kellie, the analysis of the data was entirely original, especially the background subtraction. Although the mathematical mechanism had been developed by J. D. Kellie, the criteria for this sub-traction were due to the author. This is also true for all normalizations and corrections. Interpretation of the general shape of the cross sections as well as interpretation of any apparent structure has been carried out solely by the author. The computer programmes for the theoretical calculations, including fission, neutron-capture-x-ray-emission, total scattering transmission coefficients and the final cross section calculations, have been written by the author himself, and only a code by J. D. Kellie for the calculation of the incoming wave transmission coefficients was adopted
