ON THE MOVEMENTS OF THE EARTU's CEUST. 367 



commencemeDt and the last part of the cycles, when the meau value of 

 the eccentricity was small, the sea retreated far, as between the Creta- 

 ceous and the Eocene, and in the Upper Eocene and Pliocene, The notion 

 therefore presents itself with great probability that there is a^ connection 

 between the cycles in the curve representing the eccentricity of the 

 earth's orbit and what is called a geological epoch, or what has also been 

 called a " cycle " or " circle of deposition." The two Tertiary cycles 

 are as it were great stages, each composed of sixteen smaller ones. Just 

 as each of these sixteen represents a small oscillation of the sea, so does 

 each cycle represent a great oscillation ; but this great oscillation has 

 been accomplished by means of the sixteen small ones. In the same 

 way the mean value of the eccentricity rises and falls in each cycle with 

 sixteen oscillations ; it is low at the commencement of the cycle, attains 

 its greatest value in the middle of the cycle, and falls again towards the 

 close. These agreements between the cycles of the curve and the forma- 

 tions, between the arcs of the curve and the stages, and between the 

 number of the arcs' precessions and the alternations of the strata in the 

 stages wherever these coukl be checked, appear to me to be so striking 

 as to exclude the notion of an accidental coincidence, and distinctly 

 point to a causal relation. 



If we would test tlie correctness of our hypotheses by means of the 

 older formations, the following points must be borne iu mind: After in- 

 vestigating the laws of the variations of eccentricity, Geelmuyden told 

 me that it is probable that a cycle of about 1,500,000 years must appear 

 in the curve, but that without more extended investigation we can not 

 conclude that this will continue unchanged for unlimited periods. Even 

 in the calculated curve, the Cycle iii is distinguished from the other two 

 by a much lower eccentricity in the arcs 4"-9". 



If the polar compression in old times was greater, then the preces- 

 sional period was also shorter. According to Geelmuyden it would be 

 very nearly proportional to the square of the time of rotation. For ex- 

 ample, to a rotation time of sixteen hours corresponds a (synodic) pre- 

 cessional period of 10,000years, consequently only half the present period. 

 The shorter the period the less marked (other things being equal) must 

 the climatic period be, and the more indistinct the alternation of the 

 strata. 



Further, it must be remembered that in Palteozoic and Mesozoic times 

 tlie moon was probably much nearer. In that case the lunar tide was 

 much stronger, and stronger in proportion to the solar tide than at 

 present. The day was shorter, and the stronger tidal wave acted more 

 frequently. The shores were more rapidly destroyed. Deposition, no 

 doubt, took place more rapidly. Tlie sidereal day increased more 

 (piickly in length than at present. All these circumstances must have 

 had an influence upon the form of the earth, upon the distribution of 

 land and sea, u{)on tlie disi)lacement of shore-lines, upon tlie changes of 

 climate, upon the oceau-currents, upon the distribution of chemical aud 



