We have collected together in this short chapter some additional material that is relevant to atomic beams. The question of the extent to which partial specular reection occurs is important to the development of the theory of beam formation. Some care is needed with applying the correct mean velocity of atoms either within an oven, in the beam or when impinging on surfaces. Although the differences are not large, they would be relevant in precision work, such as measurements of the velocity distribution. We also need to return to the question of the distribution of atoms within a capillary tube. We need to consider the end effects, namely, that the extent that the density of atoms just within a tube is less than that of the atoms in the input container VP and that the density in the exit plane of the tube is greater than V0, the vacuum of the system into which the atomic beam emerges. There are differing expressions for the dissociation of hydrogen on hot surfaces, which are important in estimating the degree of dissociation.