p. W. Stuart- Menteath — Salt Deposits of Dax, etc. 267 



they are arranged on lines that exhibit remarkable independence 

 towards the general disposition of the visible rocks. The salt 

 deposits of the neighbouring portion of the Pyrenees exhibit a similar 

 independence, and the latest theory — that they are shovelled from the- 

 mountains by vast processes of superficial charriage — is a recognition 

 of the general result of observation thus admitted. It coincides 

 practically with the view of Dufrenoy, of anomalous and eruptive 

 origin, for which I have long vainly claimed respect. 



But in the treatment of salt deposits it is impracticable to rely on 

 those details of arrangement which are regularly advanced as con- 

 clusive by representatives of the new theoretical geology. Every 

 mining engineer is aware that salt is practically plastic and is in 

 nearly every salt-mine subject to contortion by hydration of 

 anhydrite as well as by squeezing. In such recognition of ex- 

 perience the observations of practical engineers, such as Crouzet and 

 De Freycinet, are valuable at Dax, while much other evidence is 

 obviously out of court. The doctrine that the upper gypsum of 

 a salt-mine must be due to a different sea, and therefore to a difi"erent 

 formation, because sea-water deposits gypsum first and salt last 

 when boiled down in a pot, was gravely expounded at Cardona by 

 a foremost creator of the charriage theory in the Pyrenees and else- 

 where; but such views merely exhibit ignorance of the elements of 

 the problem as revealed by Bischof, Bunsen, Ochsenius, etc. Crouzet 

 and De Freycinet plausibly argued that the salt was bedded between 

 horizons about the junction of the Cretaceous and Tertiary as known 

 in their day. Subsequent observation tends to prove that it frequently 

 fills hollows on the surface of the Cretaceous and beneath the 

 Tertiary, the latter being of any age from the Lower Eocene to the 

 Upper Miocene, and probably even to Eecent, according to the local 

 circumstances of its deposition above the salt. Of course, no practical 

 geologist would affirm that Triassic salt may not also exist. I have 

 found it existing as the cause of salt springs at Camou, Arrigorriaga,. 

 and other places. But the actual Trias of the Pyrenees is singularly 

 unsuited to the purposes of the theorist, and he consequently com- 

 pares the Pyrenean beds he would class as such to that of Germany 

 and Lorraine. Yet in these last neither bipyramidal quartz, nor 

 arragonite, nor oligist, nor ophite are cited, and it can hardly be 

 argued that gypsum is peculiar to any special formation. 



Such being the general situation of the problem, it should be added 

 that the best exposed and most clearly related salt deposits of the 

 Pyrenees are, along the whole Spanish slope, decisively of Eocene 

 or Oligocene age. The attempts of theorists to deny this at Cardona 

 are conclusive regarding the character of their observations, while- 

 at every point they have treated on the French slope they have 

 admittedly urged the contrary of what they to-day propound. 



The main difficulty at Dax and elsewhere lies in the thick mantle of 

 marine, fluviatile, and seolian sands which cover the surface of the- 

 plain, and, accumulating to even hundreds of feet in thickness, drowns 

 the ancient valleys and extends across the plateaux of the Pyrenean 

 roots. These sands are so obviously undistinguishable in detail, and 



