HOW TO WORK IK THE ARCH^AN ROCKS. 33 



The strike of a series has often been used as an aid in correlation, 

 and, within due limits, it decidedly adds to the weight of other 

 evidence. 



In conclusion, it is to be observed that in Archaean work the proof 

 is generally cumulative. Results are often obtained by the accumula- 

 tion of minute facts, most of which cainiot be published, or even 

 recorded without incalculable labour. Each tap of the hammer helps 

 to build up the conclusion. Different lines of evidence, each of which 

 taken alone would fail to convince, converge towards the final issue. 

 TJiorourjh and detailed labour is above all necessary. With patience 

 and zeal there is no reason why the Archaean fields of work, barren as 

 they appeared to our predecessors, should not yield most fruitful 

 additions to our knowledge of the early historj- of the globe. 



