1870.] 233 [Shaler. 



and soil containing humus, through which the water percolating be- 

 comes charged with carbonic acid ; then the phosphate layer ; immedi- 

 ately beneath that the marl containing phosphates, which is only 

 slightly permeable to water. Soaking over this marl the water be- 

 comes charged with carbonate of lime and some phosphate which it 

 carries away in the drainage system of the country. This process, 

 going on for centuries, gradually dissolves away a great thickness of 

 the marl, and gives, as in the capping bed, an accumulation made up 

 of fossils from the wasted beds, which resisted decay, and could not be 

 washed away; of phosphates which became aggregated into nodules; 

 of remains of man and other recent animals, which, falling in the 

 swamp, sank through the soft bog and became trampled in among the 

 nodules by the living animals which inhabited this low land. 



Great freshets might lay down several feet of clay and sand, or 

 some rearranged marl on top of the phosphate layer, thus confusing 

 the record, by making the remains of man and extinct animals asso- 

 ciated with his early history in this region, seem a part of the ancient 

 marl beds. 



Looking upon the phosphate layer as the debris of a large amount 

 of eroded marl, it is no longer a difficult matter to account for the 

 association of fossils found there, which would be inexplicable with- 

 out some theory of this kind. 



Although this view of the derivation of the phosphate beds capping 

 the Ashley River marls seems to clear away a part of the doubt which 

 hides their origin, it discloses another question which is about as diffi- 

 cult to settle. If we are to derive the phosphates from the marl, 

 in what manner are we to account for the presence of this material in 

 the latter beds? I cannot say that I feel any great satisfaction in tne 

 explanation which I am about to offer, which after all is only half an 

 explanation ; but inasmuch as it promises to cast some light on what 

 is a rather dark subject, I venture to present it. 



It may be premised that the whole question of the formation of 

 phosphates is one of the little understood provinces of geological in- 

 quiry. The usual supposition of the vertebrate origin of these accu- 

 mulations does not fit some of the most conspicuous examples, and the 

 ingenious hypothesis of the able chemist and geologist, Mr. T. Sterry 

 Hunt, which accounts for the origin of the massive apatite beds of 

 the early palaeozoic by the action of quantities of unarticulated 

 Brachiopods, separating phosphate of lime from the water of the sea, 

 though doubtless a true cause, is not competent to explain many cases 



