and some other Stratified Deposits in the North of Scotland. 315 



same dark gray colour with the slate itself; but after exposure to atmospheric 

 influence they generally acquire a purplish blue tinge^ whilst the surrounding- 

 matrix is externally changed to a light brown. 



No icthyologist has yet determined the family to which these very sin- 

 gular remains belong. Having forwarded specimens of two or three distinct 

 species to Baron Cuvier, I shall not upon this occasion say more respecting 

 them ; but may here state generally, that the red sandstone of Caithness,, the 

 lamellar limestone, and the schists containing the fish, have all strong resem- 

 blances to the copper slate of Thuringia and its associates, and may probably 

 prove to be the equivalents of that formation ; whilst the fish, though not of the 

 same species, may belong to the same family as those found at Mansfeldt. 



Whatever may be our conclusions respecting this deposit, the preceding- 

 pages afford, it is hoped, a good exemplification of the value of the geological 

 evidence to be derived from organic remains ; since the existence of strata, 

 which must be regarded as the representatives of a large portion of the oolitic 

 series of England, has been clearly shown by the identification of their shells 

 and vegetables, although at the extremes of that series in Great Britain the 

 mineralogical character of the beds is perfectly distinct. 



Concluding Remarks. 



The following remarks, which are of a nature partly theoretical and partly 

 practical, appear to flow naturally from the facts detailed in the preceding 

 paper. 



1. A constancy in the mineralogical character, and the order of superposi- 

 tion of the strata of any country, are undoubtedly the first facts upon which 

 its geological structure must be determined. That the great deposits superior 

 to the carboniferous order are capable of being divided into groups; that 

 many of these groups range in the form of natural terraces from one side of 

 our island to the other ; that even their subordinate beds preserve through con- 

 siderable portions of their range, a great uniformity of structure and of exter- 

 nal character ; — are facts now established by a great accumulation of direct 

 evidence. It would not perhaps be too much to assert, that the physical struc- 

 ture of many parts of England might be determined by these characters alone, 

 without the help of any zoological considerations. But the foundation for a 

 true arrangement of our strata being once established, we are by no means 

 precluded from the use of any other characters with which nature may supply 

 us. The organic remains imbedded in the successive secondary strata are not 

 only essential to all theoretical speculations, but enable us to determine the 

 true place of many deposits in districts where we have not the advantage of 



