15 1- PAIuEONTOLOGY 



wards formed in those impressions. The faculty of interpreting 

 has been still more racked by similar evidences of more extra- 

 ordinary footprints, probably of large batrachian reptiles, first 

 noticed in 1834 at Hildberghausen in Saxony, in sandstones 

 of the same geological age as those in Scotland. 



The vast number and variety of such impressions, due 

 either to physical or meteoric forces, to dead organic bodies, 

 parts or products, or to the transitory actions of living 

 beings, nave at length raised up a distinct branch of palaeonto- 

 logical research, to which the term "Ichnology" has been given. 



In this class of evidences the impressions called " protich- 

 nites"* (fig. 64), left upon the "Potsdam sandstones"! of the 

 older Silurian age in Canada, are the most ancient ; but the 

 footprints of birds surpass all others in regard to their num- 

 ber, distinctness, and variety of sorts. 



But how, it may be asked, are such, footprints preserved ? 

 A common mode may be witnessed daily on those shores 

 where the tide runs high, and the sea-bottom is well adapted 

 to receive and retain the impressions made upon it at low- 

 water. 



Dr. Gould of Boston, U. S., first called the attention of natu- 

 ralists to this interesting operation on the shores of the Bay of 

 Fundy, where the tide is said to rise in some places seventy 

 feet in height. The particles deposited by that immense tidal 

 wave are derived from the destruction of previously existing 

 rocks, and consist of silicious (flinty) and micaceous (talcky) 

 particles, cemented together by calcareous (limy) or argillaceous 

 (clayey) paste, containing salts of soda, especially the muriate 

 (common salt), and coloured with various shades of the oxide or 

 rust of iron, of which the red oxide predominates. The perfection 

 of the surface forreceiving and retaining an impression depends 



: Sec Owen, "Description of (lie Impressions and Footprints of tlie Pro- 

 ticlinites from the Potsdam Sandstone of Canada," Quarterly Journal of the 

 (in. logical Society, 1852, p. 214. f Logan, ibid, p. 2. 



