95 



and consists of a layer, usually from six to fifteen inches in thickness 

 charged with nodules of calcic ]>ho3phate and containing also bones^ 

 teeth and shells, the pores of which have been more or less completely 

 filled with the same material. This deposit lies at no great depth below 

 the surface, and is still nearly horizontal. In some places it is below 

 high-water mark, and Urge quantities of the phosphatic nodules are 

 obtained by dredging in some of the estuaries and channels which 

 penetrate the low alluvial country. Where the noiule-bed occurs above 

 the sea level it is worked by a system of trenching, tlie finer material 

 being washed away on gratings, and the nodules then dried — generally 

 by artificial heat — before being sent to the mill. 



A long way farther back in time are the "Coprolite" beds of the 

 south of England, which date in fact from the Cretaceous period. 

 Where this deposit occurs at an inconsiderable depth below the surface, 

 it is worked by a system of trenching similar to that employed in 

 Carolina, the soil being carefully put to one side and subsequently 

 restored, and the land again brought under tillage. As the deposits are 

 thin, it does not i)ay to follow them to any great depth, but some years 

 ago the annual product was as much as 25,000 tons. 



These can be considered only as instances of the mode of occur- 

 rence of phosphatic materials in the geological series. Deposits more 

 or less closely analogous to those described and sufificiently rich to work 

 are found in a number of other localities, which we have not now time 

 to consider. There is reason to believe that phosphatic or "co^jrolitic'* 

 nodular deposits have bean found wherever the local conditions -were 

 favourable and large quantities of animal matter were in process of 

 accumulation and decay, throughout the entire geological series. Going 

 a great way back in geological history, we find instances of this in Canada 

 in parts of the Chazy subdivision of the Silurian, in the graptolitic 

 shales ot the Quebec group, and even in the Cambrian rocks of St. 

 John. It is true that none of these deposits are of importance from 

 an economic point of view; for instances of workaVjle deposits in these 

 palaeozoic rocks we must turn elsewhere. They are merely mentioned 

 hei'e for the purpose of connecting the occurrence of naturally concen- 

 trated phosphatic materials as found in the newer rocks, with the 

 deposits of the same material found in the oldest known rocks — those 

 cf the Laurentian period. 



