398 RETROSPECT OF THE OOLITIC SYSTEM. CHAP. 



are frequently formed in extensive horizontal beds composed of 

 laminse or smaller beds inclined about 30. In Gloucestershire 

 the lower rags of the Great oolite have this character extensively. 

 It is due to watery movement at small depths. When this move- 

 ment has drifted matter very uniformly in one direction,, the result 

 is a bed with laminae, all parallel but inclined : where the current 

 changed or admitted of eddies, the deposits vary accordingly. 

 These phaenomena, called 'false-bedding,' are very instructive as 

 to the conditions under which the oolitic rocks were accumulated. 

 Very similar deposits happen at present where affluents enter lakes 

 and bring or disperse gravelly and sandy materials on the bed. 

 Thus have been formed some deltas, especially the lower gravelly 

 parts. Such deposits are now in progress in the Lake of Geneva, 

 where the Rhone enters it, and they may be seen occasionally 

 produced in transitory forms of small extent on our sea coasts. 



Veins of calcite, regular or quite irregularly branched, appear 

 in most parts of the * freestone ' beds, as at Taynton, and somewhat 

 impede the action of the toothed saw by which this stone is neatly 

 and cheaply cut. Calcite occurs also freely crystallized in joints 

 of the rock and in cavities from which shells or corals have been 

 dissolved away; and this substance often, with quartz and oxide 

 of iron more rarely, are found lining cavities in the shells of 

 cephalopoda. Sulphate of strontian, finely crystallized, said to have 

 been found in a vein near Handborough Junction, was placed in 

 my hands in 1854. 



The changes of organic life in such a basin of the sea, unaffected 

 by great disturbances, may be considered with reference to causes 

 known to be influential in modern nature ; as, for instance, depth 

 of water, distance from shore, and quality of ' ground,' or sea- 

 bottom ; and in relation to time, which hardly enters as an element 

 into modern zoology. 



It happens in the cases before us that quality of ground and 

 depth of water go pretty closely together with distance from shore ; 

 greater depth and removal from shore with the clays ; lesser depth, 

 probably nearer approach to the shore, with the sands : the least 

 depth as a rule may be ascribed to the limestones, especially those 

 parts of them which resemble or even consist of shell and coral banks. 



If then, in comparing clays of the lias with those of the Oxford 

 and Kimmeridge stages, or the sands of Midford, Studley, and 



