BLUE MUD. 71 



often overlook the real implications of many 

 facts and figures which they have learned to 

 quote glibly enough in a certain off-hand way. 

 Let me just briefly reconstruct the chief features 

 of this scarcely recognised world's chronology 

 as I sit on this piece of fallen chalk at the foot 

 of the mouldering cliff, where the stream from 

 the meadow above brought down the newest 

 landslip during the hard frosts of last Decem- 

 ber. First of all, there is the vast lapse of 

 time represented by the Laurentian rocks of 

 Canada. These Laurentian rocks, the oldest 

 in the world, are at least 30,000 feet in thick- 

 ness, and it must be allowed that it takes a 

 reasonable number of years to accumulate 

 such a mass of solid limestone or clay as 

 that at the bottom of even the widest pri- 

 maeval ocean. In these rocks there are no 

 fossils, except a single very doubtful member 

 of the very lowest animal type. But there 

 are indirect traces of life in the shape of 

 limestone probably derived from shells, and of 

 black lead probably derived from plants. All 



