534 



SALT. 



American 

 talt forma 

 tion. 



the lake of St. Mark. The salt is of a reddish or pur- 

 ple colour, and is as hard as stone. A portion of it is 

 vashed down by the dews, and becomes as v.-hite as 

 snow, losing the sharp bitterness of the parent rock. 



In the mountains of Levotaiah and Miniss, the salt 

 is of a grey blui'h colour, and very agreeable to the 

 palate. The salt from the lake of St. Mark is of the 

 same quality, and the principal stratum of it resembles 

 a tesselated pavement, composed of various small cubes 

 of common salt. 



On both sides of the Atlas mountains it occurs in 

 great quantities. M. Hornemann discovered a plain on 

 a limestone range, which consisted of a mass of rock 

 salt, extending so far in length that no eye could reach 

 its termination, and at the same time several miles in 

 width. In Abyssinia, there is a plain of salt four days 

 journey across. 



The American salt formation, according to Dr. Van 

 Rensselaer, extends over the continent from the Alle- 

 ghany mountains to the North Pacific, between 31 and 

 4,5 of north latitude. In this immense tract rock 

 salt has been occasionally found ; but the extent of the 

 formation is inferred from the brine springs. 



In California, rock salt is found in large quantities. 

 On the plains east of the Rocky Mountains, it is 

 found in incrustations covering lands of some extent. 



The immediate valley of the Canadian river is 

 bounded by precipices of red sand rock, forming the 

 river Bluffs. In the valley b'etween these, incrustations 

 of nearly pure salt is found covering the surface to a 

 great extent like thin ice, and giving it the appearance 

 of a coating of snow when seen at a distance. 



In South America the salt mines are numerous. 

 There are many in Peru situated at the height of 

 10,000 feet, and some of them are near Potosi, where 

 the salt is usually of a violet colour, and occurring in 

 hard, solid, and continuous rocks. It also occurs in 

 Mexico, Chili, New Granada, &c. It is found in im- 

 mense blocks in the muriatiferous clay, lying above 

 sandstone, at Punta Araya, on the Cordilleras ; and at 

 the bottom of the lake Pennon Blanco, in Mexico, there 

 is a bed of clay containing about thirteen per cent, of 

 rock salt. The salt lake of Pennon Blanco yields an- 

 nually 250,000 fanegas of unpurified salt of 400 Ibs. 

 each. 



In North America, salt does not seem to have been 

 found in the state of rock. It is found, however, in in- 

 crustations of considerable thickness and solidity on 

 the soil of plains and prairies near the sources of the 

 Arkansas river ; and at Fort Osage, there is an exten- 

 sive plain 280 miles south-west from the fort, which, 

 in dry and hot weather, is covered with an incrustation 

 of clear white salt, from two to six inches thick. This 

 saline is about thirty miles in circumference, and is in 

 many places covered with drift wood. 



Having thus given an account of the principal loca- 

 lities of rock salt, we shall conclude this part of the 

 subject with some observations on the origin of this 

 mineral, for which we have been indebted to Dr. Van 

 Rensselaer. 



" As to the origin of rock salt, the most satisfactory 

 hypothesis is the supposition of its being deposited 

 from sea ; or by the desiccation of salt lakes formerly 

 covering our present continents. The objection that 

 the composition of rock salt is more pure than that 

 from the sea water, which contains also sulphate and 

 muriate of magnesia, sulphate and muriate of lime, and 

 sulphate of soda, is invalidated by the recollection that 

 viiatever impurities may exist in sea water, still, if the 



process of evaporation be conducted very slowly, the 

 crystals are nearly pure. In some places the process v 

 is conducted so well, as at Lymington, in England, 

 where it takes twelve days, that from the most impure, 

 or mother water, it still contains only twelve parts in 

 the 1000, or little more than one per cent, of impuri- 

 ties. If, then, the desiccation of lakes, or basins filled 

 with salt water, be very slow, as it must be when the 

 process is to be finished by natural evaporation, the 

 muriate of soda would be crystallized before the other 

 salts, which being more deliquescent, might be sepa- 

 rated and washed away. In the same way, the gyp- 

 sum that usually accompanies salt might be deposited, 

 and being nearly insoluble would remain. 



That lakes of salt and fresh water have once covered 

 much land, is not to be doubted in the face of so many 

 incontrovertible facts as can be brought forward. Our 

 own day offers proofs of the changes that are constant- 

 ly taking place on the earth's surface, by the desicca- 

 tion of lakes, in whatever manner accomplished. Our 

 own country, with our immense lakes or inland seas, 

 will one day exhibit a different picture to the eye of 

 the geographer, the painter, and the geologist, from 

 what it offers at present. If, as may readily be sup- 

 posed, a vast lake once covered that portion of our 

 country to the west of the Alleghany mountains, and 

 which was eventually drawn off by the outlets cut by 

 the St. Lawrence and the Hudson, through the High- 

 lands of Montreal and New York, we have an idea 

 upon a grand scale of what will, at some future day, be 

 the effect of draining our northern lakes. The falls of 

 Niagara, gradually receding to the outlet of Erie, will 

 eventually discharge the waters of the great lake and 

 its tributary streams into Ontario, to dash rapidly down 

 the St. Lawrence to the Atlantic, or to be distributed 

 slowly as from a reservoir. 



The bed of Erie will then form an extensive, plain 

 or valley, bounded by the distant hills, and watered 

 by a small lake or river, which will give passage to the 

 St. Clair and Huron, and form a piolonged channel to 

 the river Detroit. Here the geologists of future pe- 

 riods will find a fresh water formation in successive 

 strata upon the limestone bed. These strata will pro- 

 bably be a coarse sandstone with argillaceous marl, 

 containing fresh water shells ; among others, some of 

 the Uniones, so well described by Mr. Barnes. These 

 will be sedimentary fresh water formations, produ- 

 ced almost entirely by mechanical means, i. e. the de- 

 position of earthy matters, coarse or fine, envelop- 

 ing organized bodies. They may have a different 

 structure from other fresh water formations. The 

 layers may be distinct and numerous, with a coarse 

 sandy grain, having the usual perforations to manifest 

 the extrication of gas from the limestone beneath. It 

 may be similar to the fresh water formations of Paris 

 and Rome ; or may resemble the mulasse of Switzer- 

 land. 



But we need not look either into ancient records, 

 or into futurity, to know that both Fait and fresh wa- 

 ter lakes have covered much of the earth ; and that 

 they have, and do, and, from analogy, will form de- 

 posits of soils and minerals. Salt lakes still exist 

 in many places. The zout pans, in the south of 

 Africa, are salt lakes furnishing that country with 

 salt. Some of them are more famous than others ; but 

 all are situate on a plain, at a considerable elevation 

 above the sea, none being less than one hundred feet 

 above it. A brief account of one will suffice for the 

 rest. The greatest part of the bottom of the lake is 

 5 



Snlt. 



