4F0 Transactions. 



posits consist almost entirely of nodules which are composed 

 of phosphatized animal matter, while those in the neighbour- 

 hood of Taplow and Lewes* are phosphatic chalks of sediment- 

 ary origin. Those of the Somme in Francef are also chalk- 

 deposits, the phosphate being " a sedimentary chalk derived 

 from the disintegration of a vast granitic phosphatic continent." 

 Near Mons, in Belgium, J the phosphate-deposits are also with 

 Cretaceous chalk. They consist of a coarse-grained rock formed 

 of a mixture of grains of calcite and small-sized pebbles of 

 phosphate ; they are due to a concentration by water of a lime- 

 stone originally containing a small amount of lime-phosphate. 

 In Algeria and Tunis§ the phosphates occur in nodules in marl 

 or as phosphatic limestone. 



Though not precisely similar to any other known deposit, 

 the Clarendon-Millburn phosphate bears greatest resemblance to 

 those of Florida, U.S.A. The local phosphate, however, con- 

 tains only a trace of fluorine, and has no shell-traces ; the cal- 

 careous rock does not become highly phosphatic in depth ; and 

 the mode of origin is different from either of the two theories 

 advanced to explain the Florida deposits. In all these points 

 it differs from the Florida phosphate, so that, after all, the simi- 

 larity is not so very marked. 



Mining and Treatment. — At Round Hill quarry the phosphate 

 is blasted out with gelignite, the holes for the charges being 

 very difficult to bore, on account of the hard nature of the rock. 

 Very little hand-sorting takes place in the quarry, the rock 

 being immediately loaded into trucks or " boxes " and drawn 

 to the burning-ground, where it is built up with broadleaf timber 

 into large piles. The burning extends throughout several days, 

 and deprives the rock of its moisture, thus rendering it brittle 

 so that it can be more easily pulverised, and also effecting a 

 small saving in the cost of its railway carriage to Burnside, a 

 few miles south of Dunedin, where sotne of it is treated with a 

 spray of dilute sulphuric acid to partly convert it into super- 

 phosphate of lime. This chemically treated phosphate com- 

 mands a higher price than the phosphate which has not been 

 so treated. The former is more rapid in its effect on the crops, 

 as the superphosphate is at once ready for assimilation by 

 plants, while the phosphate in the crude, unsprayed rock has 



* Teall, Proc. Geol. Assoc, vol. xvi, p. 369. 



t Henri Laone, " Sur l'Origine ties Phosphates de Chaux de la 

 Somme" (1903). 



% Penrose, U.S. Geol. Surv Bull. 46, p. 105. Cornet, Quart. Journ. 

 Geol. Soc. (1886), vol. xlii, p. 325. 



§ Park, Trans. N.Z. Inst. (1902), vol. xxxv, p. 400. 



