The liaison de Cordes, invented by Battel, a Savoyard, is another very simple and effective contrivance, described by Mr. Bakewell, in the before•men tioned work, and is, perhaps, better worthy of introduction into our columns than the detail, of the Melton d'Epines, already briefly noticed. It is forty yards in length, and eleven wide ; the roof is supported upon six arches of stone-work, the intermediate space on the sides being left open. In every one of these divisions are twelve hundred cords, in rows of twenty-four each, sus pended from the roof, and tight at bottom.
The cords are about sixteen feet in length. The water is raised to a reservoir at the top of the building, and distributed into a number of small transverse canals, each row of twenty-four cords having one of these canals over it, which is so pierced as to admit the water to trickle down each separate cord, drop by drop. The original intention of this building was to crystallize the salt itself upon the cords, for which purpose the water was made use of from the pans, after it had deposited a quantity of salt in the first boiling ; to save the expense of fuel on a second boiling, the residue water of the first boiling, by repeatedly passing over the cords, deposited all its salt in about forty-five days; and the cords were incrusted with a cylinder of pure salt, which was broken off by a particular instrument for this purpose. This process is at present abandoned for crystallizing; but the cords are still used for evaporating, and are found to answer better for the higher concentration of the water than the faggots. This method did not answer for the first evaporation, because the water rotted the cords ; but it was discovered that the cords were not soon injured by it, when it had acquired five degrees of strength. The cords, Mr. Bakewell was informed, had many of them remained thirty years in use without being changed ; indeed, they were so thickly encased with depositions of selenite, that they were defended from the action of the water. This mode of evaporating is found to be more expeditious than that of the faggots. In the Maims de Cordes the evaporation goes on more speedily in windy weather than in the Maison d'Epines, as might be expected from the more ready access of air to the surface of the water.
The cords are double, passing over horizontal rods of wood at the top and the bottom, to keep them firm in their positions, and at regular distances from each other. Mr. Bakewell did not see the cords without their envelope of selenite,
but was informed that they were not thicker than the finger. With the incrus tation, they were become as thick as the wrist.
Under the head of EVAPORATION, we have explained the principle of the operation, and described a variety of very ingenious apparatus, of proved effi cacy, to which the reader is now referred. In this place we shall bring under the consideration of the reader several recently patented improvements in machinery of the same kind, but of diversified forms, expressly designed for the manufacture of salt on the great scale.
The specification of Messrs. Jump and Court's patent informs us, that the ordinary method of obtaining salt is by evaporating the saline fluid in extensive shallow pans, heated by fires and flues underneath ; that these pans are supplied with the water in a cold state, the repeated effusion of which materially checks the evaporation ; and that their improved method consists in heating and con centrating the silt water, by a simple arrangement previous to its entering the pans. For this purpose the reservoir of salt water is elevated above the pans, and the pipe which supplies them with the brine first passes through all the furnaces beneath, which brings the liquid quickly to a boiling temperature, in which state it is discharged, by means of a curved pipe, into the pans above, thereby placed facilitating and abridging the process of concentration. A stop cock is in the supply-pipe, so that, as often as it is desired to replenish the pan, this cock is opened, and the superincumbent pressure of the water in the reservoir forces out the boiling brine from the pipe into the pan, the pipe receiving, in lieu thereof, the cold hquid from the reservoir.
Mr. Johnson, of Droitwich, according to his patent of 1827, employs steam of different degrees of heat to produce the evaporation in pans inclosed from the atmosphere, so that the vapour arising from, the first pan, where the las salt is produced, is employed in heating the second, where the broad salt is formed ; and the vapour arising from the latter is employed in like manner, to produce in the third pan British bay-salt.