Excisability of plant and machinery assembled at site: attracts central excise duty when marketable and movable. The Board orders that plant and machinery assembled and erected at site attract central excise duty when the assembled article is a final product distinct from its components, is specified as excisable in the Central Excise Tariff, qualifies as goods by being movable and saleable despite attachment for operational efficiency, and is marketable even if removal and dismantling are required.