ORIGIN OF GYPSUM AND SALT DEPOSITS 255 



It is certain, being a matter of present observable process, that some 

 salt and gypsum deposits are produced by evaporation of saline waters, 

 and it is therefore a legitimate theory that all similar deposits have the 

 same origin ; but some salt deposits are so thick and pure and so local- 

 ized that no satisfactory explanation has been given of the formative 

 conditions under the evaporation process. The Stassfurt deposits are 

 some 1,200 feet in depth, and the lowest beds hold 625 feet of pure salt. 

 At Sperenberg, near Berlin, the deposits are said to have been pierced 

 4,200 feet without reaching their base. At Wieliczka the salt deposit is 

 4,600 feet thick. A mass of salt is described at Parajd, Transylvania, 

 with length 7,550 feet, breadth 5,576 feet, and depth 590 feet. When 

 we consider that 93 per cent of the volume of sea water must be evapo- 

 rated in order to throw down the salt, it is difficult to imagine the phys- 

 ical conditions of either sea or lake which could precipitate such local- 

 ized masses in such pure state. The remarkably deep and pure deposits 

 at Petite Anse, in the Mississippi delta, are still unexplained. 



Salt masses sometimes contain inclusions of hydrocarbons, hydrogen, 

 carbon dioxide, and nitrogen, which strongly suggests the association 

 found in volcanic emanations. 



The aridity of climate necessary for the production of salt deposits 

 by evaporation must be taken into the account, and salt masses are found 

 in strata as far back as the Cambrian. This fact seems positively incon- 

 sistent with the factors of climate required by the old hypothesis, as will 

 be noted later. 



It may be possible wholly to explain the salt deposits under the evap- 

 oration theory, but if so it is time it were done. The delay and diffi- 

 culty suggest the wisdom of trying a new line of attack. 



Geologic Climates 



While climatology is immediately a province of meteorology, under 

 the new hypothesis, which we are favoring, not only the origin of the 

 atmosphere, but its subsequent changes in composition, producing cli- 

 matal variations, are due to geologic processes. The new geology involves 

 a new meteorology. Instead of the highly carbonated atmosphere and 

 tropical climate of early geologic time, according to the old hypothesis, 

 with slow decarbonation and cooling, culminating in the refrigeration of 

 the present day and pointing to a " final winter," we shall regard the 

 past climatic conditions as not radically unlike those of the present. 

 We shall recognize that throughout geologic time there have been such 

 variations in climate, periods of cold and aridity, or of heat and moisture, 

 as we know have occurred since the Middle Tertiary. The paleontologic 



