458 ON THE SUCCESSIVE FORM 



mate strata; as an interval of* repose, apparently much 

 longer, of the surface of the earth, is also proved hy 

 the consecutive arrangement of any series: while the 

 extent of the series in question thus also gives an 

 approximation to the length of that period of rest. 

 This rule however is suhject to exceptions: but they 

 are such as do not vitiate its value. As formerly 

 shown, from the mode in which elevated strata lie, 

 those which succeed to them must often he parallel 

 or consecutive, as well as reverse; and this double 

 relation may even take place within very small spaces. 

 In such cases, the interruption is determined by any 

 tract, however small, of a reversed position; or by 

 other parts of the relative characters of the two ap- 

 proximate series, on which it would now be super- 

 fluous to enlarge. 



Now although these reversals of position indicate 

 a revolution at that particular spot, they do not prove 

 that such changes were universal or extensive. The 

 extent of these is to be judged of by other circum- 

 stances and principally by the extensive range oc- 

 cupied by the inferior and by the superior strata; 

 as will be more fully shown, when the number and 

 nature of these probable revolutions shall come under 

 review. 



If there are many cases of revolution which can 

 thus be proved by a comparison of the positions of 

 approximate strata alone, there is one, at least, for 

 which we must resort solely to other evidence. In 

 many instances, this evidence is interesting, even 

 where it may be superfluous ; while, in some, it serves 

 to indicate that which mere change of position does 

 riot, namely the magnitude and extent of the revo- 

 lution, and, that within undefineable limits, a long 



