Ch. VI . ] 



OF ANCIENT DEPOSITS. 



115 



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names 



That these were often inappropriate was admitted ; but the 

 student was taught to understand them in no other than a 

 chronological sense; so that the Chalk might be a grey quartz- 

 ose sandstone devoid of calcareous matter, as near Dresden, 

 or a hard, compact, and sometimes flaggy limestone, as in 

 parts of the Alps, or a brown sandstone or green marl, as in 



Jersey, U. S. In like manner, the Green Sand, it was 



New Jersey, TJ. S. 



said, is often represented 



limestone and other mineral 



masses entirely devoid of green grains. So the Oolitic tex- 

 ture was declared to be rather an exception than otherwise 

 to the general rule in rocks of the Oolitic period, and to be 

 found in strata both of older and newer date ; and it often 

 became necessary to affirm that no particle of carbonaceous 

 matter conld be detected in districts where the true Coal 

 series abounded. In spite of every precaution the habitual 

 use of this language could scarcely fail to instil into the liiind 

 of the pupil an idea that chalk, coal, salt, red marl, or the 

 Oolitic structure were far more widely characteristic of the 

 rocks of a given age than was really the case. 



There is still another cause of deception, disposing us to 

 ascribe a more limited range to the newer sedimentary forma- 

 tions as compared to the older, namely, the very general 

 concealment of the newer strata beneath the waters of lakes 

 and seas, and the wide exposure above waters of the more 

 ancient. The Chalk, for example, now seen stretching for 

 thousands of miles over different parts of Europe, has become 

 visible to us by the effect, not of one, but of many distinct 

 series of subterranean movements. Time has been required, 

 and a succession of geological periods, to raise it above the 

 waves in so many regions ; and if calcareous rocks of the 

 middle and upper tertiary periods have been formed, as 

 homogeneous in mineral composition throughout equally ex- 

 tensive regions, it may require convulsions as numerous as all 

 those which have occurred since the origin of the Chalk to 

 bring them up within the sphere of human observation. 

 Hence the rocks of more modern periods may appear partial, 

 as compared to those of remoter eras, not because of any 



original inferiority in their extent, but because there has not 



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