Artificial dams should be made long before they are required, and be dug in clay if possible. Dimensions will vary, but a depth of 4 ft. should not be exceeded, and the area should be divided among several, rather than restricted to a few of large size. The average crop of 1 acre will require a dam of about the following capacity :—Length, 50 ft. ; breadth, 9 ft. ; depth, 4 ft. The situation should be sheltered from wind, with a sunny aspect. Soundness is essential in a dam; flax-water will escape mere readily than clean water. Peat-beg holes may be extemporized as dams, but they must be of old formation. New dams should be dug during winter, and old ones repaired at the same season; either should be filled by surface drainage, and kept full till steep ing time. Where the dams are so situated as to allow the water to be run off, a pipe may be fixed in the bottom or side for that purpose ; the same water should never be used twice.
Dams and water being suitably provided, the retting commences. The beets, tied as described, are taken to the dam. The flax pulled each day should be put into the dam on the same evening if possible ; and one day's pulling should never be mixed with that of another. Beginning at one end of the dam, the beets are laid closely side by side in rows, with the root end down ; when one row is finished, a second is commenced, placing the tops of these beets level with the bands of the first, and so on, row after row, till the dam is full ; a final layer may be placed flat on the top. The whole is then covered with ragweeds, rushes, or straw, then preferably with boards ; and finally stones, or turf-sods with the grass downwards, are piled on to sink the flax beneath the surface of the water. Where a stock dam is available, by far the best plan is to fill the dam while dry, and then let in the water. Fermentation ensues, the sooner the better; in continued warm weather, it will set in immediately. This process causes the flax to rise above the water ; it must be forced down, and more heavily weighted. When the fermentation decreases, the flax will sink in the water ; the weight must then be partially removed, so as to allow the flax to rise to the heat, but never so far as to reach above the water. After a few days,—the duration of the retting varies exceedingly, according to the nature of the weather, of the water, and of the crop,—the flax is examined, and the greatest judgment is demanded to decide when the watering has proceeded suffi ciently far. One or two beets are removed from different portions of the dam, opened, and tested. The conditions which indicate that the flax is ready to leave the dam are as follows :—If " glit " appears in the middle of the beet, and it feels soft when grasped in the hand; if the "reeds" or stems taken out are covered with a greenish slimy substance, and if this can be removed by delicately passing the reed between the finger and thumb ; and if, when gently bent over the forefinger, the woody " chive " or core freely separates from the fibre, and starts up. The stem must be examined
throughout its length ; it will be found softer at the root-end, but if it yields to these tests in the middle, it may safely be considered ready. Both coarse and fine stems must be selected ; the former will be ready first, so the average condition must be determined. The Dutch test is to hold the middle of a stem in both hands, and twist in opposite directions ; if the fibre separates freely from the core, the operation is considered complete. It is common to ret flax too little, trusting to finish the process on the grass ; but this is not advisable, and the grassing should amount to little more than drying. At first, examination should be repeated daily, then at intervals of six hours, as the change may be rapid towards the end. When the retting is complete, the burden is removed, and the beets are taken out very carefully by men standing in the water. The flax is then allowed to drain for a few hours, either by laying the bundles down on an incline, or by standing them together on their root ends, taking care not to place too many together, or heating may result.
Many plans have been devised for avoiding the retting process altogether, but none has yet met with even partial success. Later investigations have been prosecuted rather in the direction of reducing the time occupied in the operation as ordinarily conducted, and rendering it more constant and uniform. The only successful modifications are the following :—(1) R. B. Schenk's warm water system. Open pools and dams are replaced by large, covered, wooden vats, in which the flax is tightly packed in a vertical position. The water admitted is raised to a temperature of 24°-35° F.), and is maintained at that heat during the whole period of steeping. The fermen tation is very brisk, and the operation is concluded in 50-60 hours. (2) Pownall supplements this by passing the stems, immediately on their removal from the vat, between heavy rollers, over which a stream of clean water is kept flowing, this effectually washing away the adherent gummy matters, and much facilitating subsequent processes. (3) Michael Andrews suggests, as an improvement upon Schenk's method, to admit the water at the proper temperature, and then to maintain it so by keeping the air of the chamber containing the vat at the correct degree, uniformity being by this means much more easily ensured. The ordinary Irish method of retting in open pools of stagnant water is unequalled by any in simplicity, and cheapness of plant ; but some of the Con tinental methods are more elaborate, and produce better fibre. These will be alluded to below, under the section treating of local modifications.