The problems arising in framing an Excise Act are very different from those met with in the Customs. It has been shown that for the purposes of Customs control, all foreign trade is concentrated through authorized channels, and the assessment and collection of duties can be carried out under a few general rules, applicable to all goods. The collection of excise duties on commodities demands official cognisance before production begins, and sometimes before various stages in production are entered upon. The law in relation to the manufacture of beer for sale illustrates most of principles of Excise administration. The essential features of brewing consist of infusing materials such as malted barley with hot water, draining off the liquid, which is the unfermented beer conducting it to a collecting vessel and adding yeast to set up fermentation. The Excise supervision of manufactures is sometimes supplemented by a control over the trading of product. The chief instances occur with tobacco and alcohol.