Page:The Harveian oration - delivered at the Royal College of Physicians, London, June 29th, 1867 (IA b22315263).pdf/19

Rh Collateral science is further aiding us to perceive that there is a different molecular arrangement in diaphanous or isolating bodies, as compared with opaque or conducting bodies, such as metals, etc. How far the new discoveries of Graham, which have demonstrated the presence of gases in metals and other substances held there by what he terms "occlusion," may throw light on this interesting and intricate subject, is as yet problematical; but I must add that the power, by means of heat, of making metals give up large volumes of these occluded gases, proves the existence of spaces between the molecules capable of