The extent of the submergence and the area over which the Palaeozoic strata were deposited are unknown; for in consequence of renewed elevation without deformation, erosion in later periods has stripped off an undetermined amount of the covering strata.
This is the method of undetermined coefficients.
It seems quite evident that the city of Assur was originally founded by Semites from Babylonia at quite an early, but as yet undetermined date.
The cause of this condition is still undetermined.
In this list, while certain occurrences in rocks of undetermined age in little-known regions have been omitted, many of those included are of merely academic interest, and a still larger number indicate fields supplying at present only local needs.