240 Canadian Record of Science. 



stone, a, bit of iron pyrites, a shell or a crystal of carbonate 

 of lime. Negative evidence, however, is strong. I think 

 it safe to say, that many concretions have no nucleus of 

 foreign matter. If one exist, it is in the form of such a 

 minute, grain of calcium carbonate, it cannot be detected 

 with the eye. 



Under the direction of Prof. W. O. Crosby, a concretion 

 was sawed in two and polished. Lines of stratification were 

 distinctly seen, but with this exception the mass was per- 

 fectly homogeneous. There was not the slightest evidence 

 of a nucleus or of concentric structure. One half was 

 sawed in two again, giving a sharp angle, which proved the 

 extreme fineness of the material. A quarter was etched in 

 chlorhydric acid, and while this rendered evident a concen- 

 tric structure, it did not reveal a nucleus. Little spherical 

 cavities were seen, as if the tendency to concretionary 

 structure was so great that the concreting material was not 

 satisfied with forming one large concretion, and so made 

 smaller ones within the larger. I also dissolved one clay- 

 stone in acid, and examined the insoluble residue upon a 

 filter. It was impalpably fine clay, and no foreign particle 

 of any appreciable size was visible. 



Prof. Hitchcock says : " In no case in Massachusetts have 

 I seen an organic relic as a nucleus." In 1859 Mr. Charles 

 Stodder exhibited, at a meeting of the Boston Society of 

 Natural History, two specimens cut open, one showing a 

 nucleus less than 1-16 of an inch in diameter, the other not. 

 At the same meeting ex-President Bouve' remarked while 

 showing some concretions: "These bodies do not always 

 have a nucleus ; on the contrary, those from many localities 

 very seldom have any. These seem by no means necessary 

 for their production." I have looked through the Proceed- 

 ings of the Society since 1859, but find nothing that throws 

 additional light upon the subject. 



The third question involves the history of a claystone. 

 We first have the clay arranged in layers by the mechanical 

 action of water. That the formation of the concretions is 

 subsequent to the deposition of the clay is proved by the 



