SALT MANUFACTURE IN HONG KONG
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When the brine in the ponds is completely dry, a coating of salt is deposited on the bottom, which is scraped into piles by means of a wooden scraper, one side of which is sharpened to facilitate thorough scraping, and is then carried to the company for sale.
The leached soil in the vat, after the sea-water has percolated through and washed out the salt, is then carried back into the field; any clods are pulverised, and the fine soil is spread out to be re-impregnated with salt.
II. THE ORDINARY SOLAR PROCESS.
This method has only recently been introduced into Tai O when the farmers from Swabue were first engaged by the salt companies.* The process differs from the method described above in that, instead of impregnating the soil with salt and leaching it to obtain a saturated brine, a series of concentrating ponds are constructed for the same purpose. The basins are constructed adjoining the Tai O bay and are divided into several small ponds by low ridges of mud of about 8 to 10 inches in height. In order to establish a condition under which the sea-water from one pond may flow into the other by gravity, the ponds are not on the same level, one being about 2 to 3 inches higher than the other next to it, and one end being also higher than the other end of the same pond, so that brine may be run from the first to the last continuously by gravity. They are arranged in groups with five ponds in each, Figure 4. Four ponds of each unit group are used for concentrating the brine, and the last is for drying or crystallization. All the ponds must be levelled, cleaned, and hardened by rolling with a heavy stone-roller; the crystallization ponds, however, are paved with small pebbles and lime and then hardened by rolling with the heavy stone-roller. This layer of smooth pebbles prevents the admixture of the sand, or mud, with the salt.
Large reservoir ponds, like the ordinary fish-ponds, or simply narrow canals varying from several inches to two or three feet in depth, are constructed in the space between the basins and the enclosing dyke, or between the various groups of the basins.
Sea-water from the bay is first admitted to the reservoir-ponds through canals communicating with the bay at high tide.
*But see Rev. Mr Krone's article in this number of the Journal at p. 199. Ed.
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