December 27, 1889.] 



SCIENCE. 



445 



the material for his map in 1850, when the water was at its lowest 

 stage, and the latter in the spring of 1869, when the water was 

 near its highest stage. The one map shows an area of 1,750, and 

 the other of 2,166, square miles. From these I estimate the old 

 mean area at 1,820 miles, and the new at 2,125 miles, and the in- 

 crease at 305 miles, or 17 per cent." 



The probable cause of this increased water-supply in the Great 

 Basin would form a most interesting and instructive subject of 

 inquiry, but such would be foreign to the purposes of the present 

 paper; and here it must suffice to say, that two theories have been 

 advanced as offering most probable explanations of the phenome- 

 non ; viz., the climatic theory, and the theory of human agencies. 

 In the report already referred to (" Lands of the Arid Regions ") 

 the author says, " On the whole, it may be wise to hold the ques- 

 tion an open one, whether the water-supply has been increased by 

 a climatic change, or by human agency. So far as we now know, 

 neither theory is inconsistent with the facts, and it is possible that 

 the truth includes both." 



During this recent epoch of increasing volume, the lake-water 

 would be naturally expected to show a far lower percentage of 

 solid contents. In " Contributions to the History of Lake Bonne- 

 ville," published in the " Report of the United States Geological 

 Survey, 1880-81," Gilbert places the total salinity of the water at 

 fifteen per cent, — a striking variation from the figures of Dr. Gale, 

 yet a variation not at all too great to be fully explained by the in- 

 creased volume of the lake, and the consequent decrease in con- 

 centration. An investigation of the water by Allen in 1869 (see 

 King's report) showed the total solid matter to be 14.9934 per 

 cent. The present writer made an analysis on water taken from 

 the lake in December, 1885, with the following results : — 



Sodium chloride (Na CI) 



Sodium sulpliate (Na^ SO4) ... 

 Magnesium chloride (Mg CI2) . . 

 Calcium sulphate (Ca SO,). . . 

 Potassium sulphate (Kg SO4). 

 Total solid matter 



This water had a specific gravity of 1.1225. Another sample of 

 lake-water taken in February, 1888, showed a density of 1.1261. 

 A further test was made in June, 1889, the water being 1.148 in 

 density ; and in August, 1889, the water was 1.1569. The figures 

 resulting from the latest determinations show a considerable in- 

 crease in the proportion of solids ; and this is fully explained by 

 the succession of excessively dry seasons to which the Great Basin 

 has been subjected since 1883, causing a remarkable shrinking of 

 the lake volume. In August, 1S89, the lake was lower than at 

 any time since the inauguration of ' Gilbert's " new r^z'w^." A 

 sample of water was taken from the lake during that month, and 

 analyzed, with these results. The water possessed a specific 

 gravity of 1.1569, and contained, — 



Sodium chloride (Na CI) 



Sodium sulphate (Nas SO,). ., 

 Magnesium chloride (Mg CI 2) 

 Calcium sulphate (Ca SO4) . . . 

 Potassium sulphate (Ks SO4) 

 Total solids 



Grams 

 per Litre. 



226.263 



Per Cent by 

 Weight. 



15-7430 

 1.0502 



19.5576 



It would be a difficult task indeed to determine the mean com- 

 position of the lake. Its waters rise and fall, and become more 

 concentrated or dilute, according to the conditions controlling the 

 rates of supply and evaporation. The latest analysis reported 



above, indicating 19.5576 per cent solid matter, though itisacloser 

 approach than usual to the earliest figures, and the ones most 

 widely published, is hardly to be considered typical, since the sea- 

 son of 1889 was one of unusual drought. Two or three consecu- 

 tive winters with heavy snows would dilute the water to its con- 

 dition of a few years ago. In the opinion of the writer, it would 

 be more correct to quote the average contents of the Salt Lake 

 water at sixteen per cent solid matters than at twenty-two per cent, 

 as is most frequently done. 



Our subject presents an economical aspect which is well worthy 

 of attentive consideration. The composition of the water is such 

 as to suggest the easy manufacture of a number of chemical sub- 

 stances therefrom. Branches of such an enterprise have already 

 been instituted, and the results achieved have kindled the brightest 

 hopes of increasing success. 



The preparation of common salt from the water would be natu- 

 rally the first undertaking of the kind to suggest itself ; and this 

 process has been in successful operation on an industrial scale for 

 a number of years. There are now half a dozen establishments 

 for salt-manufacture on the lake shore. At several of these places, 

 however, the preparations for salt-making consist simply in con- 

 structing a number of evaporating-ponds below the level of the 

 lake, and separated from the latter by dikes of such a height that 

 during periods of rough water the waves beat over the embank- 

 ments, and fill the ponds with brine. The evaporation of the water 

 thus enclosed goes on without any artificial aid, and a bountiful 

 harvest of salt in the season thereof is the result. In such cases 

 the evaporation is carried to completion. All the solid constituents 

 of the brine remain in the salt, there being no attempt made to get 

 rid of the mother-liquors after the deposit of crystals. 



At other of the works, however, notably at the Inland Salt Com- 

 pany's Gardens, a different plan is pursued. This establishment is 

 the largest salt-works in the West, and is situated near Garfield 

 Beach, the most popular pleasure-resort on the lake. The method 

 employed by this company differs from those already described in 

 that the water is pumped from the lake into ponds prepared for its 

 reception, and situated above the level of the lake surface. The 

 mother-liquors flow off — are returned to the lake, in fact — when 

 the evaporation has reached the proper stage. From the establish- 

 ment of the works until 1883 the lake was close to the ponds ; but, 

 owing to the unusually high rate of evaporation attending the dry 

 seasons of the immediate past, the water has receded, so that at 

 present it has to be conveyed over 2,500 feet to the evaporating re- 

 ceptacles. This is effected by the aid of two centrifugal pumps, 

 raising together 14,000 gallons of water per minute. The pumps 

 throw the water to a height of fourteen feet, into a flume, through 

 which it flows to the ponds. These are nine in number, and are 

 arranged in series. In the first pond the mechanically suspended 

 matters are left as sediment or scum, and the water passes into the 

 second in a clear condition. The ponds cover upwards of a thou- 

 sand acres, and the drain channels leading from them aggregate 

 nine miles in length. The pumping continues through May, June, 

 and July. A fair idea of the rate of evaporation in the thirsty 

 atmosphere of the Great Basin may be gained from contemplating 

 the fact that to supply the volume of water disappearing from the 

 ponds by evaporation requires the action of the pumps ten hours 

 daily in June and July. This is equal to the carrying away of 

 8,400,000 gallons per day from the surface of the ponds. 



The " salt harvest " begins in August, soon after the cessation 

 of pumping, and continues till all is gathered, frequently extending 

 into the spring months of the succeeding year. An average season 

 yields a layer of salt seven inches deep, which amount would be 

 deposited from forty-nine inches of lake-water. The density at 

 which salt begins to deposit, as observed at the ponds, and con- 

 firmed by laboratory experiments, is 1.2 121, and that of the escap- 

 ing mother-liquors is 1.2345. The yield of salt is at the rate of 150 

 tons per inch depth per acre. The crop is gathered on horse-cars 

 which run on movable tracks into the ponds. At the works the 

 operations are simple and effective. A link-belt conveyor carries 

 the coarse salt to the crusher, thence to the dryer, after which a 

 sifting process is employed by which the salt is separated into table 

 salt and dair)' salt. 



It will be seen from the foregoing that the preparation of salt 



