Cast iron glazing bars

2080. The material of fixed roofs is generally iron, as being less bulky in proportion to the strength required, most durable, and admitting, in the case of curvilinear roofs, a curvature to be formed at less expense than it could be of timber. In these roofs, in general, no other bare or opaque bearers are required than those for receiving the glass; and hence their simplicity and unity with regard to component parts, and the equal degree of transparency in every part of the surface.