138 



THE ULTIMATE SOURCE 



and is considered by the G-eological Survey to belong to the 

 Eocene period. The salt rocks of the Pyrenees are also 

 Eocene. In the Austrian Alps the salt is in the older Oolitic 

 record. In Switzerland it is older again in the Lias. In 

 Wiirtemberg it is in the Muschelkalk. In England the salt 

 mines are in the New Red Sandstone, but many salt springs 

 issue from the Carboniferous rocks, which are older still. In 

 China, Burmah, and at Bakur on the Caspian, salt springs are 

 associated with springs of mineral oil and naphtha, supposed 

 to originate also in the Coal measures. The salt rocks of the 

 Alleghany Mountains, Washington Co., Virginia, U.S., are 

 Silurian. A salt spring at Keswick rises from the lowest 

 division of the salt rocks of Cumberland, in the Lower Silurian. 

 And the Cis-Indus, or Indian salt range proper, to which 

 the Mayo mines belong, is the oldest of all, the oldest mine 

 discovered in the world, being covered over by Silurian strata. 

 It would be, in the present state of our knowledge, useless 

 to speculate as to the age of the Mayo salt mines. Many 

 thousands of years separate our time from that of the formation 

 of the Wieliczka salt mine, the most recent of the series 

 enumerated. Intervals of thousands of years separate the 

 members of the series, one from another, and the Mayo salt 

 mine must be hundreds of thousands of years old. It is at 

 the very furthest extremity of the geological record, and its 

 formation may be said to be coincident with the beginnings 

 of life on our planet. So much for the age of rock salt 

 deposits that are known, and whose ages have been determined. 

 Other undiscovered rock salt formations doubtless exist, 

 whose ages we have no means of ascertaining. 



It may be fairly inferred, as a conclusion from the foregoing, 

 that rock salt has been forming, in an intermittent way, 

 throughout all knowledgable time, from the Pre- Silurian period 

 to the Tertiary ; but that the Silurian and Carboniferous periods 

 were the most prolific in such deposits. There is no evidence, 



