A. Lindenkohl — Post-glacial Subsidence, etc. 489- 



mium amalgam, distilled in a current of hydrogen, gives a 

 similar result if the temperature is not raised too high. The 

 enormous affinity which these forms of metals exhibit for 

 oxygen renders their study very difficult. It has not been 

 before suggested that their activity is due to their being atomic,, 

 but this would seem to be a much more rational explanation 

 than that of extreme division.* A broad distinction must of 

 course be drawn between chemical and mechanical division : a 

 substance may be atomic and yet appear in masses : may be in 

 the finest mechanical division and yet be molecular or poly- 

 merized. Silver being a metal with a very low affinity for 

 oxygen could not be expected to show in the. atomic state the 

 same inflammability as more oxidable metals. 



In conclusion it may be said that there is much reason to 

 suppose that elements may exist in the atomic form and that 

 allotropic silver may present such a case. This is of course 

 far from being proved and is offered only as a " working 

 hypothesis." As such it may afford a useful aid in further 

 investigations. 



Philadelphia, April, 1891. 



Art. LIX. — Notes on the sub-marine channel of the Htcdson 

 River and other evidences of Post-glacial Subsidence of the 

 Middle Atlantic Coast Region' by A. Lindenkohl. 

 With Plate XVIII. 



The American Journal of Science of 188of contained an 

 article by the writer entitled " Geology of the Sea Bottom in 

 the Approaches to New York Bay," in which a description was 

 given of a remarkable depression in the sea bottom off Sandy 

 Hook and an attempt was also made to account for the origin 

 of this depression and to trace its connection with the geology 

 of the adjacent coast region. 



Professor Dana, who was the first to recognize the true shape 

 of this depression and to direct attention to its existence by a 

 map and reference in his " Manual of Geology," published in 

 1863, takes up the subject again in a recent number of this 

 Journal, J treating of Long Island in the Quaternary with obser- 

 vations on the sub-marine Hudson River channel, and carefully 



* M. Cr. Rousseau, in the new Encyclopedic Chimique, seems to entirely aban- 

 don the old view of extreme division and considers these forms to be allotropic 

 and comparable with the allotropic forms of phosphorus, etc. Vol. hi, page 56. 



f Vol xxix, pp. 475 et seq., also republished as Appendix No. ]3, U. S. Coast 

 and Geodetic Survey, Report of 1884. 



% Vol. xl, pp. 425-437. 



