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crystallising pans to a depth of about 3 inches. Sometimes the "lunari" replenishes his pans three or four times, sometimes he is content with the salt crop derived from one filling. When the crop is ready, the mother liquor is run off on to the neighbouring ground. The salt crystals are scraped from the floor of the pan with wooden scrapers, washed with brine from a well, accumulated in small heaps and, after passing inspection, stored in large heaps in the open.
The trenches are not a mere accessory to the construction of the protecting embankment. Being filled at spring tide every fortnight, they act to some extent as a supply reservoir and, by keeping up the hydraulic head, increase the flow of brine in the wells. At the time of my visit (August, 1924) the concentration in the trenches varied between 8° and 13.5° Baumé that of sea water at the shore was 3° Baumé-so that they serve as useful condensers, subsidiary to the normal sea water seepage
With a climate such as that of Maurypur seepage of fresh water from the low hills on the landward side is negligible; all the seepage is from the sea.
The purpose of my visit was to advise on a proposed increase in production. For several years the works have been producing from 11,000 tons to 16,000 tons of salt per annum. Three private companies proposed to lease from Government about 1,600 acres in neighbouring areas, increasing the production to 200,000 tons per annum, and the Commissioner in Sind wished to know if the resources available could maintain this.
Function of the tre aches.
Proposed increased production.
On new sites outside the present works practically saturated brine is found to a depth of about 6 feet, and below this less concentrated brine is said to be found. If we assume a porosity of 25 per cent for the upper 6 feet of soil, we might expect from the brine already in situ an immediate output of the order of 1,000 tons per acre. Such an output, however, cou'd not be kept up. The concentration of the brine would gradually diminish, until it reached a condition of equilibrium dependent on many factors such as distance from seepage supply and rates of flow, evaporation and removal. Although it is not possible to calculate the resultant of these factors, we do have some evidence of their ultimate effect. One half of the works has been running for only a few years,
but the other 90 acres have been producing since 1878. During these 46 years their average annual output has been 109 tons per acre, and the production shows no signs of falling off. We may assume that a condition of equilibrium between production and brine supply from the sea has been reached in these old works, and that, with similar conditions, like areas would be permanently capable of producing the same amount. For a supply of 200,000 tons of salt per annum each of the 1,800 acres would have to produce 111 tons. There seems to be no reason to doubt their capacity, for the beach is remarkably regular throughout this area. In the new ground this figure might be far exceeded for several years, but, if the removal of the concentrated brine were too rapid, production might be seriously curtailed.
It appears to me that with such favourable climatic and tidal conditions the question of evaporation direct from sea water through condensers should be considered, for the exSuggested changes. pense of the necessary earthworks would probably be much less than that involved in sinking the huge number of wells required under the present system. South and southwest of the present works, too, is a large, shallow backwater, connected by a narrow creek to Karachi harbour. It is from the tidal overflow of this backwater that the salt works are periodically supplied. If a dam were built across the narrow part of the creek, the backwater might be used as a reservoir for the condensers and might even be used as a preliminary condenser itself.
Whatever method of salt recovery may be used, an effort should be made to get rid of the present pernicious system of allowing all mother liquors to remain in the area of manufacture.
INDEX TO RECORDS, VOLUME LVI.
Additions to collections
Afghanistan, Cretaceous fossils from
Alum, statistics of
Amber, statistics of
Amherst district, ore deposits
Analyses, Burmese lignites
Annandale, N. and Hora, S. L., a Fresh-water Fish from the
Arakan Coast, Burma, submarine mud eruptions
Arakan-Naga region, mineral deposits
Aravalli system, Kishengarh
Asbestos, statistics of
Bawdwin, silver-lead deposits
Bawzaing lead-copper ores
Belgaum, dam site
Bithynia tentaculata, (Linn.) var. Kashmirensis
Blanford, W. T., Cretaceous fossils collected by
Bhattacharji, D. S.
Bihar and Orissa, Railway Alignment
Bion, H. S., Cretaceous fossils from Afghanistan and Khorasan
191, 192, 193.
365, 367, 368, 369.
201, 202, 203.
66, 67, 68-74.
6, 8, 12.
7, 8, 36, 44.