78 TRANSFORMATIONS OF ROCK-MATTER. 



vast succession of stratified rocks of true sedimentary origin 

 like any of the later systems, but so altered "by mineral 

 transformation that it is only in localities where the meta- 

 morphism has been partial and less intense that evidence 

 of their aqueous and fossiliferous nature can possibly be 

 discovered. As the extensive and mountainous tracts in 

 which these schists occur have been but slenderly investi- 

 gated, subsequent research may yet discover other fossils, 

 and resolve the whole into definite and satisfactory life- 

 systems. And should such hopes be fulfilled, how incon- 

 ceivably exalted will our notions of the world's antiquity 

 become new aeons of life and physical activity extending 

 away into a past as vast perhaps in duration as all the 

 later ages that geology has revealed ! We can never hope 

 to read aright these earlier pages of world-history, but 

 passages here and there may be recovered, and from these 

 scattered hints we may obtain enough to convince that 

 then as now the physical agencies of nature were ever 

 active and subject to the same laws, and that Life too was 

 present as their accompaniment, though then merely com- 

 ing into view under the operation of a higher and more 

 complicated law of development. 



How then, it may be asked, are we to deal, in a chrono- 

 logical point of view, with the metamorphic rocks in which 

 no fossils have been detected ? Shall we describe them as 

 altered Silurians, Cambrians, or Laurentians? or shall we 

 continue to regard them merely as metamorphic strata of 

 unknown age, till some organism has been discovered that 

 may lead to their identification 1 Where the stratigraphical 

 succession is evident, it may often be convenient to mark 

 them as Silurian, or Cambrian, or Laurentian ; but where 

 the succession is doubtful, and no trace of organism has 

 been discovered, it will be much safer still to retain them as 

 mere metamorphic strata. Much error, both in theory and 



