92 THE PRIMABY PERIODS. 



certainly not the highest of their respective orders, neither 

 are they exactly the lowest ; but, making ample allowance 

 for the defects of our present information, it may "be safely 

 asserted that the fauna or animal-life of the Cambrian 

 period is altogether one of a lowly character, and that of the 

 flora or plant-life we know nothing beyond a few indistinct 

 impressions of algse or sea-weeds. Even the little we now 

 know of the Cambrian flora and fauna was altogether un- 

 known twenty years ago, and it is chiefly since 1846, and 

 more especially since 1859, that its fossiliferous character 

 has been fairly established. 



Here then, as in the case of the Laurentian system, we 

 have a long period of the earth's history so long that 

 18,000 or 20,000 feet of sediment was accumulated in cer- 

 tain parts of the ocean and of which we know nothing 

 beyond what is recorded by these marine strata and the fos- 

 sils they contain. We have no glimpse of the land from 

 which these sediments were worn and wasted, yet there 

 must have been broad lands to supply this waste and rivers 

 to transport it. We are utterly ignorant of the plant-life 

 and animal-life if terrestrial life then existed by which 

 these lands were peopled. We know nothing of the dispo- 

 sition of sea and land as compared with the existing conti- 

 nents and seas. All that we clearly perceive is the exist- 

 ence of these sediment-receiving oceans, with their scattered 

 sea-weeds, zoophytes, shell-fish, and Crustacea, and only 

 faintly and at distant intervals their sandy and muddy 

 shores, in which annelids bored and left their burrows, and 

 over which Crustacea tracked and left their traces. Little 

 as this knowledge may seem, it is everything compared with 

 the beliefs of our ancestors; it is a great deal compared 

 with what was known even by the last generation ; and 

 it holds out the encouragement that another generation, 

 by following in the right path, will arrive at a fuller in- 



