In some regions, notably in the Baltic province and in parts of the United States, the rocks still retain their original horizontality of deposition, the muds are scarcely indurated and the sands are still incoherent; but in most parts of the world they bear abundant evidence of the many movements and stresses to which they have been exposed through so enormous a period of time.
The rocks in the Arakan range and its spurs are metamorphic, and comprise clay, slates, ironstone and indurated sandstone; towards the S., ironstone, trap and rocks of basaltic character are common; veins of steatite and white fibrous quartz are also found.
Next in antiquity to hydraulic lime is Roman cement, prepared by heating an indurated marl occurring naturally in nodules.
It was worked for about a hundred years in only its upper bed, but in 1781, after traversing a layer of indurated clay intersected with small veins of salt 102 yds.
In 1779 three beds of rock-salt were discovered at Lawton, separated from one another by layers of indurated clay.
Normally the pleon carries six pairs of two-branched appendages, of which the first three are much articulated flexible swimming feet, the last three few-jointed comparatively indurated uropods.
The Dakota formation is largely sandstone, which gives rise to hogbacks where it has been tilted, indurated and exposed to erosion along the eastern base of the Rocky Mountains.