384 ON THE OCCURRENCE OF PHOSPHATES 



Mr. Koch inquired whether any Yivianite had been obtained by 

 Mr. Hicks. 



Prof. Seelet thought that the paper, interesting as it was, did 

 not bring ns any nearer to the source of the phosphate of lime in 

 phosphatic deposits, especially such as those recently described by 

 Mr. Davies as occurring in the Bala beds. The proportion of phos- 

 phoric acid in the ash of the lobster did not appear to be greater 

 than in that of plants; and whilst the debris of marine animals 

 would be rapidly dispersed, those of seaweeds would remain at the 

 bottom, and it was to these that he was inclined to attribute the 

 accumulation of phosphate of lime in these deposits. At the same 

 time he believed that the phosphoric acid was primarily derived 

 from volcanic rocks, out of which the phosphates have been washed 

 by water. The great proportion of phosphate of lime in the shell of 

 the Trilobite was probably due to infiltration. 



Mr. Hughes said that he had examined many soils in Australia 

 and elsewhere, and that when the soil was deficient in phosphate of 

 lime the underlying rock was the same, but when the soil was rich 

 in phosphate the rock also contained it. He had also found phos- 

 phoric acid in igneous rocks from the north of England and 

 Scotland. 



Mr. Topley inquired as to the amount of phosphoric acid in the 

 flesh of the lobster. He remarked that the shells of the Gault 

 were largely phosphatized, and that they seem to have drawn their 

 phosphoric acid from the surrounding rock. There are many phos- 

 phatic nodules in the lower part of the Gault, and also on the surface 

 of the Kentish rag. 



Mr. Hicks, in reply, said he thought it possible that water, or 

 rather watery vapour, may have washed out the phosphate of lime 

 from the altered beds ; but he contended that this must have taken 

 place at the time the intrusions occurred, for at present these beds 

 are as solid and impervious to water as are the beds in which the 

 phosphate of lime is now present. He stated that he did not intend 

 to say that there were no contemporaneous traps of so old a date as 

 the Menevian beds, but that there were none in "Wales of earlier 

 date than the Arenig or Llandeilo series ; he had even mentioned 

 that there were some in Canada of the age of the Laurentian rocks ; 

 but as there was no evidence of any of these in Wales, we could not 

 look upon the phosphate of lime in these beds as having been ob- 

 tained from dissolved apatite. In reply to Prof. Seeley, he said he 

 could not allow that some beds lost all their phosphate of lime by 

 percolation of water, and that the fossils in the others obtained it 

 by the same means. He did not suppose, however, that all the 

 phosphate of lime present in the fossil shell occurred in the natural 

 shell ; and he believed that it had to some extent in the process of 

 fossilization replaced carbonate of lime. 



Mr. Htjdleston, in reply to Mr. Topley first, said that his calcu- 

 lations of the percentage of phosphoric acid in the lobster were 

 based upon the amount compared with the total contents of the 

 animal itself, as this seemed the most suitable for purposes of 



