OF COMMON SALT. 



165 



Next, to make use of KrummePs cubic miles, we must have the quantity 

 of salt in a cubic measure of our sea water having the specific gravity 1-024. 

 It so happens that a cubic foot of distilled water weighs at 60° F. 1,000 

 ounces. At the same temperature and pressure a cubic foot of the sea 

 water, specific gravity 1*024, would weigh 1,024 ounces. As we have seen 

 that it contains 2-378 per cent, by weight of salt, we may calculate on 24'350 

 ounces of salt to the cubic foot of sea. Here I drop the decimal *350 of an 

 ounce to the cubic foot, as a further check on exaggeration. Dr. Warth states 

 that a cubic foot of Mayo mine rock salt weighs 93 lb. or 1,488 , ounces. It 

 would, therefore, require about 62 cubic feet of this sea to yield a cubic foot 

 of rock salt. 



There are 147,197,952,000 cubic feet in a cubic mile. A cubic mile of the 

 sea water would therefore yield 2,574,160,516 cubic feet of rock salt. If 

 we multiply this by the number of cubic miles in the ocean and divide the 

 resultant by the number of cubic feet in a mile, we get the number of cubic 

 miles of rock salt in the sea. KrummePs researches show that the volume 

 of the entire sea is 3,138,000 cubic miles. The number of marine surveys 

 which have been made of late years would enable this calculation to be made 

 with some approach to accuracy. 



2,374,160,516 X 3,138,000 _ 



50,612. 



147,197,952,000 



"We thus get 50,612 cubic miles of rock salt in the sea at the present time. 



Before passing on to make a rough estimate of the amount of salt which 

 has been removed from the sea by solid rock salt formations, it is as well 

 to notice Herschel's estimate of the weight of the ocean. Herschel calculated 

 that the entire sea contained 2,494,500 billions of tons of sea water. 



At 23-78, or for the sake of round numbers 24 per mille, of sodic chloride, 

 by weight, this would yield 24,000,000 tons per billion. Multiply this by 

 the number of billions and divide by the number of tons in a cubic mile of 

 solid rock salt, viz., 6,111,339,079, at 93 lb. to the cubic foot, we get — 



24,000,000 X 2,494,500 Mn „ ^ „ , , 

 5 111 339 079 = 9 ><97 cubic miles of rock salt. 



It will be seen that these two estimates are widely different, the last being 

 less than one-fifth of the first. I mention it, however, merely as a matter 

 of curiosity, as KrummePs recent researches are undoubtedly entitled to most 

 weight. 



Of the other calculation, regarding the amount of rock salt which has been 

 separated from the sea, there is, after all, very little to disclose. I start 

 with Dr. Warth's estimate of 10 cubic miles of salt in the Cis-Indus salt 

 range. The area of the range is 670 square miles and the average depth of 

 the salt deposit is about 200 feet. It varies according to Mr. Wynn from 

 100 to 275 feet. If the salt lay 200 feet thick all over this area, the cubical 

 contents would be 26 cubic miles. The salt occupies more than one-third of 

 the whole area. The area of the Trans-Indus salt range is 1,000 square 

 miles. Mr. Wynn calculates that one-fifth of this region or 200 square miles 

 is taken up with salt. The depth of the deposit varies, but it reaches in some 

 places 1,200 feet : say that it averages 500, and we get a cubical contents of 

 20 cubic miles of rock salt. The Carpathian salt region occupies an area of 

 50,000 square miles. The salt, to judge by the map, which shows salt mines 

 at wide intervals, would occupy about one-fifteenth of this area, or 3,333 

 square miles. Its depth in some places is very great, over 1,200 feet; it 

 may be assumed to average 600 feet in thickness; this would give us 416 

 cubic miles of rock salt. The English salt-bearing region occupies about 450 

 square miles. Taking one-third of it as salt deposit, with an average 



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