187 



valuable stone : so that new phaenomena are continually brought to 

 light, and as rapidly defaced, during the course of the operations at 

 the quarries. 



A paper was afterwards read, entitled "Observations on the Ich- 

 thyolites of Gamrie in Banffshire, and on the accompanying Red Con- 

 glomerates and Sandstones," by Joseph Prestwich, Jun., Esq., F.G.S. 



In the summer of 1826, Mr, J. Christie of Banff, in company with 

 Mr. Dockar of Findon, discovered the thin stratum of clay which 

 contains the Gamrie ichthyolites, previously noticed in the bed of a 

 small brook ; but as those gentlemen did not determine the geolo- 

 gical situation of the stratum, the author, at the suggestion of Mr. 

 Murchison, undertook, in a recent visit to Scotland, to investigate 

 its relative position. 



The formations of which the district consists are, micaceous and 

 argillaceous schists, old red sandstone, a red conglomerate, and lias 

 clay and sand. 



The bed containing the ichthyolites the author found to belong to 

 the upper part of the red conglomerate, and he gives the following 

 section of the deposit : 



Soil : 



1 . Loose conglomerate of angular fragments of argil- 



laceous schist, imbedded in a reddish brown, 

 slightly micaceous sand 35 feet. 



2. Red clay 2 



3. Grey clay, with ichthyolites disposed in nodular 



layers about six or eight inches apart 4 



4. Grey, slightly micaceous shale 12 



5. Red conglomerate of" quartz and clay slate .... 5 



6. Coarse, micaceous, deep red sandstone 3 



7. Loose conglomerate 12 



Beneath the last stratum are other beds of conglomerate, which 

 gradually become coarser and harder, and inclose a few rolled masses 

 of gneiss. 



The ichthyolites, though most abundant in the bed of grey clay 

 (No. 3.), are not confined to it, remains of fishes occurring in the 

 subjacent sandstones and conglomerates ; and it is only when the 

 sandstones are entirely replaced by the conglomerates that the fish 

 exuviae disappear. This distinction the author assigns to the apparent 

 turbulent state of the water which brought the conglomerates together, 

 and the comparatively tranquil condition of that which deposited the 

 sandy strata. 



With respect to the geological position of this system of sandstones 

 and conglomerates, the author shows that it rests unconformably on 

 the old red sandstone, and that it is overlaid by outliers of lias j he 

 is further of opinion that it belongs to the age of the coal measures, 

 and, probably, of the millstone grit. This conclusion is likewise in ac- 

 cordance with the opinion of M. Agassiz respecting the age of the 

 deposit, deduced from the characters of the ichthyolites. 



The author, in addition to this account of the bed containing the 



