lime is present, and 

 in • converted into the 



simple of the oxygen set free by the 



plan 



The g: re probably of or- 



gai. in, that ii suit from the accumulation on the 



ocean i of V. of marine organisms, 



such n- .oils of molluf iminifera and skeletons 



of c 



.e writers have put forth the theory that many limestones, 

 dally I ring n< lie remains, have been 



formed by chemical precipitation; this, it is argued, has been 

 causr.l by reaction of alkaline carbonates on lime salts, or by 

 the breaking up of bicarbonate of lime on exposure to the air, 

 this salt having been often brought to the sea in river water. 

 Dr T. Sterry Hunt was an earnest advocate of the precipitation 

 theory. 1 



G. Bischof was an active opponent of this theory, arguing 2 

 that lime carbonate would not be precipitated under the condi- 

 tions existing in sea water. To cause its precipitation in a man- 

 ner similar to gypsum, Bischof reasons that 75$ of the ocean 

 water would have to be evaporated, in order to produce sufficient 

 concentration. 



_ rains of carbonate of lime inter- 

 mingled with the Bhell fragments suggests the possibility of twi 



nic and chemical, acting at the Bame time in the 



building up of the calcareous deposits. This may. however, be 



lained by th< thai calcium carbonate crystallizes very 



linary temperatures, and thai portions of the 



ains in the Limestone may have been dissolved and re- 



•1. 



Ed. 4. 1891. p. B2, 311. Fee also, Lapparent, 

 Alt k.-M', j). (85; also /iik.i. Lehrbncfa der petro- 



: |>liys. gttA, 1 : "1. 



