DIFFICULTIES AND OBJECTIONS 223 



It must not be lost sight of, however, that in 

 such cases there may exist a large amount of 

 undeveloped and even unconscious scepticism, 

 which shows itself not in active opposition, but 

 merely in quietly ignoring this great discovery, or 

 regarding it with doubt, as an uncertain or un- 

 established point in science. Such scepticism is 

 especially to be expected on the part of the many 

 enthusiastic students of petrography who are ac- 

 customed to regard rocks merely as mineral aggre- 

 gates, and even to have their slices prepared in a 

 manner which scarcely permits organic remains of 

 present to be distinguished. Such students should 

 consider that the discovery of Eozoon brings the 

 rocks of the Laurentian system into more full 

 harmony with the other geological formations. It 

 explains the origin of the Laurentian limestones in 

 consistency with that of similar rocks in the later 

 periods, and in like manner it helps us to ac- 

 count for the graphite and sulphides and iron 

 ores of these old rocks. It shows us that no time 

 was lost in the introduction of life on the earth. 

 Otherwise there would have been a vast lapse of 

 time in which, while the conditions suitable to life 

 were probably present, no living thing existed to 



