At Valenciennes I met with Mr. Cail, who, beside being an engineer and machine-maker, is interested in sugar-making, both in France and in the West Indies, and most thoroughly understands the subject.  He invited me to accompany him to Douai, to see a new set of works which had been set agoing this month.  I was of course too glad to accept his invitation, and started with him at six next morning, reached Douai at eight, and then proceeded to the works, which are a few miles out of town.  In this work a new process is also employed; it is that of Mr. Rouseau, and is said to answer well.  The beet root juice, as soon as possible after expression, is thrown up by a montjus into copper clarifiers with double bottoms, heated by steam at a pressure of five atmospheres.  To every hundred litres of juice (=22 gals.) two kilogrammes of lime are added (about four and a half pounds English weight).  The lime is most carefully prepared and mixed with large quantities of hot water till it forms a milk perfectly free from lumps.  The steam is turned off, and the juice heated to 90 deg.  A complete defecation has taken place, the steam is shut off, and the juice left a short time, to allow the heavier impurities to subside.  It is then run off in the usual manner, undergoes a slight filtration through a cotton cloth placed over a layer of about four inches thick of animal charcoal, and runs into a second set of copper vessels placed on a lower level than the clarifiers; these vessels are heated by means of a coil of steam piping sufficient to make them boil.  A second pipe passes into them, making a single turn at the bottom of the vessel; this is pierced on the lower side with small holes, through which a stream of carbonic acid gas is forced.

    This decomposes the saccharate of lime, which has been formed in
    consequence of the large excess of lime added to the clarifiers.

The lime is precipitated as carbonate.  When precipitation has ceased, steam is turned on, and the whole made to boil; this expels any excess of carbonic acid; the liquor is then run off, undergoes a similar partial filtration to that mentioned above, and is then passed through the charcoal filters to be decomposed.  The sugar made by this process, directly from the beet-root juice, is nearly white.  The molasses is re-boiled as often as six times; each time undergoing a clarification and filtration through animal charcoal.  And the proceeds of the last re-boiling is certainly in appearance not worse than a great deal of muscovado I have seen shipped from Trinidad.

In this work there are about 150 people employed.  The work goes on night and day, one gang replacing the other.  The whole evaporation is done by two vacuum pans, each 61/2 feet in diameter, 80,000 kilogrammes of beet-root are used daily, from which about 6,000 kilogrammes of sugar are obtained, equal to about 6 tons English weight.