PRE-CAMBRIAN EVOLUTION 7 



in the Universal Review for July, 1859^ uses these 

 words : ' Only the last chapter of the earth's history has 

 come down to us. The many previous chapters, stretch- 

 ing back to a time immeasurably remote, have been 

 burnt, and with them all the records of life we may 

 presume they contained.' Indeed, so brief and unim- 

 portant does Herbert Spencer consider this last chapter 

 to have been that he is puzzled to account for ' such 

 evidences of progression as exist'; and finally concludes 

 that they are of no significance in relation to the doctrine 

 of evolution, but probably represent the succession of 

 forms by which a newly upheaved land would be peopled. 

 He argues that the earliest immigrants would be the 

 lower forms of animal and vegetable life, and that these 

 would be followed by an irregular succession of higher 

 and higher forms, which ' would thus simulate the succes- 

 sion presented by our own sedimentary series '. 



We see, then, what these three great writers on evolu- 

 tion thought on the subject : they were all convinced 

 that the time during which the geologists concluded that 

 the fossiliferous rocks had been formed was utterly 

 insufficient to account for organic evolution. 



Our object to-day is first to consider the objections 

 raised by physicists against the time demanded by the 

 geologist, and still more against its multiplication by the 

 student of organic evolution ; secondly, to inquire whether 

 the present state of palaeontological and zoological know- 

 ledge increases or diminishes the weight of the threefold 

 opinion quoted above an opinion formed on far more 

 slender evidence than that which is now available. 

 And if we find the conclusion sustained, it must be con- 

 sidered to have a very important bearing upon the 

 controversy. 



The arguments of the physicists are three : 

 First, the argument from the calculated secular change 

 in the length of the day the most important element of 

 which is due to tidal retardation. It has been known for 

 a very long time that the tides are slowly increasing the 

 1 Reprinted in his Essays, 1868, vol. i. pp. 324-76. 



