J. W. DAWSON ON THE PHOSPHATES OF CANADA. 291 



limestone, which, according to Sir William Logan's sections, is about 

 11,500 feet above the fundamental gneiss. It appears, from recent 

 observations of Mr. Ycnnor and Mr. W. T. Morris, that the bed 

 holding the Burgess Eozoon is on the same horizon with the lime- 

 stone of Grenville. The phosphates are most abundant in the beds 

 overlying this band. This gives a further presumption that the 

 collection and separation of the apatite is due to some organic 

 agency, and may indicate that animals having phosphatic skeletons 

 first became abundant after the sea-bottom had been largely occupied 

 by Eozoon. 



I would not attach too great value to the above considerations ; 

 but, taken together, and in connexion with the occurrence of apatite 

 in the Cambrian and Silurian, they seem to afford at least a 

 probability that the separation of the Laurentian phosphate from 

 the sea-water, and its accumulation in particular beds, may have 

 been due to the agency of marine life. Positive proof of this can 

 be obtained only by the recognition of organic form and structure ; 

 and for this we can scarcely hope, unless we should be so fortunate 

 as to find some portion of the Lower Laurentian series in a less 

 altered condition than that in which it occurs in the apatite districts 

 of Canada. Should such structures be found, however, it is not 

 improbable that the) r may belong to forms of life almost as much 

 lower than the Lingulce and Trilobites of the Cambrian as these are 

 inferior to the fishes and reptiles of the Mesozoic. 



Discussion. 



Mr. Hicks said that the author had traced the existence of these 

 phosphatic nodules considerably lower in America than had been 

 done in England. He was inclined to accept the view of their 

 organic origin, seeing that in England certainly the abundance of 

 phosphates depends on that of organic life. The phosphate was due 

 chiefly to the shell and to the decomposition of the substance of the 

 body of the animals. 



Mr. Keeping remarked that the presence of graphite in these rocks 

 had been ascribed to plants ; if so, the deposit was formed not far 

 from shore, and consequently we should not get that freedom from 

 sediment which is necessary for the production of an extensive de- 

 posit of animal origin. It seemed to him that attributing to these 

 deposits an animal origin was like going round to the back door when 

 the front door was open ; for there was plenty of apatite in the 

 igneous rocks. He believed that even in later ages, when life was 

 more abundant, no workable deposits of coprolite nodules had been 

 formed where now found, but they had been sifted out by the action 

 of water from older deposits ; for example, those of Cambridge from 

 the Gault, and those of the Red Crag from the London Clay. 



