SALT. 



535 



covered with one continued body of salt, like a sheet 

 of ice, the crystals so united a* to form one solid body 

 as hard as rock. The shore is similar to. the sandy 

 beach of the sea coast, covered with sandstone and 

 quart /.DM- peM>le<i. At this htaeh brains a thin cru-t 

 of salt, increa-in^ in thickness and solidity as it ad- 

 vances to the 1.1. (!d!c < f the lake. Near its margin, 

 where it is four or five inches thick, the vi!t is taken 

 out with pick-axes, and i-; lit for n-e. I he thickness 

 of this bed at tin- middle has never been ascertained, as 

 the \vateis do not subside. In endeavouring to account 

 for the iiccunuilation of pure crystallized halt at the 

 bottom of this lake, it might be considered an explana- 

 tion sufficiently sat i -factory to say, the waters on the 

 south roast of Africa contain a high proportion of salt. 

 During the strong south-east winds of summer, the sea 

 spray i> carried a great distance into the country, in 

 the shape of thick mist. The powerful and combined 

 effects of the dry wind and sun carry on a rapid evapo- 

 ration of the aqueous part of the mist, and, of course, 

 a disengagement of the saline pafticles, which fall on 

 the ground ami the foliage of the shrubbery. When 

 the rains commence, they are dissolved and carried in 

 solution to the salt pan, towards which the country on 

 everj side inclines. 



The quantity of salt thus taken from the sea, and 

 borne into the country, is so very great, that at the dis- 

 tance of many miles from the co.ist, the air is percepti- 

 bly saline when walking against it. The atmosphere is 

 obscure, anil objects at a short distance are not seen. 

 These winds last for nearly two-thirds of the whole 

 year, and it is easy to conceive, that in the lapse of 

 ages an immense accumulation of suit can thus be 

 formed. This lake is in red sandstone, and the salt is 

 in some places tinged with the red colour of the oxide 

 of iron. 



In Mexico, the salt lake of Pennon Blanco, already 

 noticed, yields annually 250,000 fanegas of unpunfled 

 salt of 400 Ibs. each, making an aggregate of about 

 1,785,714 bushels. 



Turks Islands are celebrated for salt ponds, which 

 in some years have yielded more than 30,000 tons of 

 salt for exportation. 



The occurrence of rock salt deep under the surface 

 of the earth, or high above the level of the sea, forms 

 no objection to its being a deposit from water, since 

 all geologists allow, and undoubted facts prove, that 

 the ocean once covered all the continents now known. 

 Whether the earth has been elevated above the sea, or 

 the sea depressed beneath the level of the earth, the 

 valleys must have been filled with salt water, which, 

 upon evaporation, deposited salt. At Cardona, and 

 other places, it seems to have been deposited in the 

 red sandstone, or rather to be enveloped by it. Some 

 of these valleys occur at great elevation: thus the one 

 in which is deposited the salt mine of Tyrol is 5000 

 feet above the level of the sea. In the deserts of Peru 

 is one 10,000 feet, according to Ulloa, above the sea. 

 Others again are at various depths beneath the sur- 

 face ; thus, one in England is 735 feet deep, being 420 

 feet beneath the level of the ocean. 



The difficulty which has been supposed to exist in 

 accounting for the formation of strata under which rock 

 salt is found, is in a great measure obviated by the or- 



ganic remains found in them ; proving that each stra- 

 tum wan once the uppermost and lat formed on the '*^"/^ < 

 j.'lnbe, and was in turn covered by others at different 

 and distant periods. In the same way there are many 

 strata occasionally covering coal and beds of shale, 

 abonndin ' impression*. 



The situation of -alt m l>e-U or springs at the foot of 

 mountain chains, as already mentioned, may in SOOM 

 measure tend to illustrate in formation, as it is proba- 

 ble that they (the mountain chain*) were once the 

 boundaries of inland seas or lakes, when our continents 

 and oceans bore a different relative pobition from what 

 they now exhibit."* 



4. On the Uses of Salt. 



The uses of salt are numerous and important. It is I' 

 used in the following articles of manufacture. ssle. 



" Sal ammoniac, says Dr. Van Henselaer, or mu- 

 riate of ammonia, is made in abundance from common 

 salt, which contains .01 per cent, of muriatic acid. 



The manufacture of this article was abandoned in 

 England, in consequence of the heavy duty of ' 

 ton laid on salt. In consequence, however, ot b ttern 

 from the salt works being allowed in Scotland for the 

 manufacture, the price has been reduced nearly one 

 half, and before the duty was taken off, was sold at 

 ]20 per ton. 



In the manufacture of glass, salt is largely employ- 

 ed; soda, which is procured from common sail, is used 

 for plate glass ; potash for flint glass, and common salt, 

 mixed wi h kelp, for crown-glass. 



Oxy-muriate of lime, and other oxy-muriatic salts 

 employed in bleaching,- are made from salt, and con- 

 sume a large quantity of it in the manufacture. 



Spirit of salt, or muriatic acid, requires large quanti- 

 ties of salt. Mr. Parkes consumed twenty tons yearly 

 in the production of it ; and at least 1000 tons are used 

 for this purpose in England every year. It is used in 

 a variety of processes in dyeing and calico printing. 



Glauber's salt is made from what remains in the stills 

 after the distillation of muriatic acid. This residuum 

 was formerly thrown away, until a person employed it 

 in making Glauber's salt. 



Epsom salt is produced from salt, or the evapora- 

 tion of sea water. The brine, which yields 100 tons of 

 salt, gives from four to five tons of this valuable article. 

 Dr. Henry, has discovered a process of preparing it 

 from magnesian lime.-tone, and has reduced the price 

 one half. It can be made however still cheaper from sea 

 water. Magnesia is made from salt brine, or sea water. 



Crystallized soda is also made from common salt; 

 and &". the duty is taken off salt, the importation of 

 American or Ru-sian pot and pearl ashes may be su- 

 perseded, and 10,000 tons may be used annually in 

 Great Britain. Several hundred tons are used in wash- 

 ing alone. 



Barilla of an excellent quality is made from salt. 

 In the manufacture of hard soap, salt is a necessary in- 

 gredient. 



Corrosive sublimate is always made from common 

 salt. It is not only a medicine, but is used extensive, 

 ly in calico printing, and in other arts. Salt is always 

 used in making corrosive sublimate: every 6 Ibs. of 



* Some curious discoveries respecting the consolidation of sand by the fumes of ialt or of brine, hare very recently been made by Sir 

 James Hall, Bart. A copious abstract of his very curious paper on this subject, will be found in Dr. Urewster'* Journal of Scientc, yel. iii. 

 page 1. 



