OF COMMON SALT. 



151 



that these marine specimens lived and died in the neigh- 

 bourhood, and were washed into the deep salt area, from the 

 surrounding gypsum, after salt formation had commenced. 



The most serious objection to which the aqueous hypothesis 

 is open is founded upon the abnormal position of the gypsum 

 which overlies the rock salt, at some places, instead of being 

 beneath it, as it should be theoretically, since it is much the 

 less soluble salt and the first to deposit, and since it does 

 practically lie under the salt, at all modern salt deposits which 

 have been observed, in rectangular artificial basins. This is 

 unquestionably a surprising difficulty. It is not, however, an 

 insuperable one. There are various ways of accounting for 

 the anomalous position of the gypsum, and some of these ways 

 have much force of reason and truth about them. Some argue 

 that the gypsum was originally deposited beneath the salt, but 

 that it was subsequently removed by subterranean denudation, 

 by hot springs or currents, forcing their way up from lower 

 levels. Others think that upheavals and overthrows caused 

 by the secular cooling of the earth crust, or by volcanic 

 action, of which we have much evidence in the condition of the 

 salt and other rocks, may have led to a reversal of the original 

 order of the deposit. It may be said, too, that we can hardly 

 deduce from theoretical and observed conditions, at the present 

 day, the sequence of events which took place remote ages ago, 

 when some of the conditions of soil and brine were certainly 

 different from what they are now. 



I am of opinion that the explanation is, after all, not very 

 far to seek. There is no difficulty, whatever, in accounting for 

 the presence of gypsum, on top of the salt deposit, or in strata 

 running through it. The problem lies in the absence of 

 gypsum beneath the salt. Now, as to this, gypsum is found 

 at the bottom of the salt deposit at many places which have 

 been worked out, or have been exposed in section. It is so 

 found at Ischgl in Upper Austria, at Wimpfen, in Wiirtem- 



