The absolute values of the viscosity of the gas silicane have been determined for the temperatures 15°C. and 100°C. The data have been used to calculate the mean collision area presented by the silicane molecule in the gaseous state. Use is then made of the knowledge of this dimension in an attempt to elucidate the structure of the silicane molecule in relation to those of other gaseous hydrides whose molecules have equal numbers of extra-nuclear electrons.