If we had mixed gravel and sand and desired to separate the gravel into assorted sizes and get the sand by itself, we would pass the mass through a series of sieves of gradually smaller mesh. The first sieve of course would catch all the largest pebbles, the next in size would let all the second sized gravel through, and so on until the final sieve would have separated the coarse sand from the fine. In this figure of illustration, the coarse pebbles may be taken to represent the water and the fusel oils which are mixed and partly tend to rise with the alcohol, and the alcohol may be represented as the gravel larger than the sand, and the fine sand as the etheric vapors. If this gravel were forced upwardly through a series of sieves gradually growing finer, it would be analogous figuratively to the upward passage of the vapors through a distilling column composed of plates or chambers; the water and fusel oils would be retained in the lower portion of the column and continually sent back there; the alcohol would pass into the upper chambers of the column and the ethers or fore-shots would pass out from the very fine sieve at the top of the column. The vertical chambers above each plate of the rectifying column are to-day used as the separate eliminating chambers referred to above. It has been found in practice that as before stated, each plate of a column contained upon it liquid of a certain temperature and above it vapors of a certain degree of vaporization. That is, in a continuous column fed regularly by condensation from above and supplied with a constant flow of phlegm, each plate carries upon it a liquid of constant composition relative to the boiling point of the fluid on that plate. As many extractions may thus be made from the various plates as there are different liquids to be isolated. Thus by tapping different portions of the column, vapors of different degrees of vaporization are found and may be carried off and the phlegm be thus fractionated. In the case of one column the first runnings or fore-shot would be found in the upper portion of the column to which they would have risen by reason of their degree of volatility. The last runnings or oils, aldehydes, etc., would be found in the lower portion of the column still mixed with the spirit, while upon the plates of the middle portion of the column would be found the vapor of the alcohol freed from the fusel oils and from the,ethers. It is understood, of course, throughout this description that the liquid being treated is not wash but phlegm; that is, the raw spirit containing the fusel oils, ethers, water and alcohol.