II, nr tin Hixtunj of tl" l'<i*t A' Head 



aids in reef-building. Fine shales tell of soft 

 mud washed from the adjacent shore and de- 

 posited in quiet waters, while coarse-grained 

 sandstones and coarser conglomerates were laid 

 down nearer shore, where the wash of waves 

 and sweep of tides and currents carried away 

 all finer particles, to deposit them farther out 

 at sea. 



Such is a general outline of the data avail- 

 able for writing the history of the past, and 

 such the methods by which these data have 

 been interpreted and the scattered parts woven 

 into a connected whole. That many mistakes 

 have been made in doing this is undeniable, 

 nor may we say that all have been corrected. 

 But the same may be said of any history, even 

 of the record of current events, and if errors 

 are pardonable, surely the historian may be for- 

 given who is writing of events that took place 

 not hundreds, but thousands and millions, of 

 years ago. It must be borne in mind, too, that 

 the student of the past is sadly hampered by 

 what Darwin called the imperfection of the 

 record, the titter lack of anything like a con- 

 3 25 



