208 REPORT OF NATIONAL MUSEUM, 1899. 



the surface. It is then run into the fourth and last vat, where the 

 final evaporation takes place and the salt itself crystallizes out. Care 

 must be exercised, however, lest the evaporation proceed too far, in 

 which case sulphate of soda (Glauber's salt) and other injurious sub- 

 stances will also be deposited, and the quality of the sodium chloride 

 thereby be greatly deteriorated. 



As to the capabilities of works constructed as above, it may be said 

 that during a dry season vats covering an area of 3,000 square feet 

 would evaporate about 32,500 gallons of water, thus producing some 

 100 bushels of salt and 400 pounds of Glauber's salt. The moist 

 climate of the Atlantic States, however, necessitates the roofing of 

 the vats in such a manner that they can be protected or exposed as 

 desired, thereby greatly increasing the cost of the plant. Sundry 

 parts of the Pacific coast, on the other hand, owing to their almost 

 entire freedom from rains during a large part of the year, are pecu- 

 liarly adapted for the manufacture by solar evaporation. Hence, 

 while the works on the Atlantic coast have nearly all been discon- 

 tinued, there has been a corresponding growth in the West, and par- 

 ticularly in the region about San Francisco Bay. 



The methods of procedure in the California works do not differ 

 materially from that already given, excepting that no roofs are required 

 over the vats, which are therefore made much larger. One of the 

 principal establishments in Alameda County may be described as fol- 

 lows: The works are situated upon a low marsh, naturally covered by 

 high tides. This has been divided, by means of piles driven into the 

 mud and by earth embankments, into a series of seven vats or reser- 

 voirs, all but the last of which are upon the natural surface of the 

 ground that is, without wooden or other artificial bottoms. The entire 

 area inclosed in the seven vats is about 600 acres, necessitating some 

 15 miles of levees. The season of manufacture lasts from May to 

 October. At the beginning of the spring tides, which rise some 12 to 

 15 inches above the marsh level, the fifteen gates of reservoir No. 1, com- 

 prising some 300 acres, are opened and the waters of the bay allowed 

 to flow in. In this great artifical salt lake the water is allowed to stand 

 until all the mud and filth has become precipitated, which usualty 

 requires some two weeks. Then, by means of pumps driven by wind- 

 mills, the water is driven from reservoir to reservoir as concentration 

 continues, till finally the salt crystallizes out in No. 7, and the bittern is 

 pumped back into the bay. The annual product of the works above 

 described is about 2,000 tons. 



A somewhat similar process is pursued in the manufacture of salt 

 from inland lakes as the Great Salt Lake, Utah. The following account 

 of the method here employed is by Dr. J. E. Talmage: 



The Inland Salt Company's gardens are situated near Garfield Beach, the most 

 popular pleasure resort on the lake. In the method employed the water is pumped 



