150 Rev. A. Sedgwick and Mr. Murchison on Deposits contained between 



Under Geanie's Mill are seen some grey, brownish grey, and greenish grey 

 calciferous sandstones, alternating with some bituminous, laminated, calcareous 

 beds, on one of which were some fish scales, and some fragments which ap- 

 pear to be analogous to the plates of a tortoise, resembling a Trionyx found 

 in the bituminous schist of Caithness. 



Between Geanie's Mill and Balloan Castle the phaenomena are of less interest : the beds in the 

 ascending order preserve nearly the same characters ; and in one place they contain a subordinate 

 mass of pyritous shale, which throws out a spring of fetid sulphureous water*. 



From Balloan Castle to the extreme point of Tarbet Ness, we did not remark any subordinate 

 calcareous beds like those above described, although some of the greenish grey sandstones were 

 calciferous. The general aspect and mode of weathering of the crumbling ruinous cliff reminded 

 us of many varieties of new red sandstone. Among the soft red and variegated masses were, 

 however, many strong beds of brown ironshot sandstone (at Port Mahomich, containing stains 

 of coaly matter), and of brownish grey, grey, greenish grey, and white gritstone, and micaceous 

 flagstone hardly to be distinguished from the ordinary sandstones of the carboniferous series. 



From the preceding details, we think there can be no doubt that a part of 

 the sandstone series in Easter Ross and Cromarty (especially that portion of 

 it above described betwen the North Sutor and Balloan Castle), must be 

 identified with the middle system of deposits of Caithness. And after a careful 

 examination of all the phasnomena, we were disposed to identify the series of 

 beds to the north of Balloan Castle with the sandstones of Dunnet Head on 

 the Pentland Firth. 



In Caithness, three great subdivisions of the secondary deposits are natural 

 and well defined ; for the flagstone series forms a complete physical separa- 

 tion between the lower conglomerates and the upper red sandstones. But, on 

 the Murray Firth these divisions are in some measure arbitrary ; for the cal- 

 careous beds are entirely subordinate to the various sandstones, and produce 

 no change in the general aspect of the cliffs, or in the natural features of the 

 country. Hence, even allowing the classification we are attempting to esta- 

 blish, it is perhaps impossible to draw a precise line between the middle and 

 upper system of the sandstone series of Ross-shire. 



3. Transverse Sections of the Secondary Sijstem on the Southern Shores of 



the Murray Firth. ^ 



We think it necessary briefly to notice some of these sections, although the 

 coarse conglomerates have on this part of the coast thinned off", and nearly 



* The calciferous portions which appear in this part of the coast are generally concretionary, 

 and may often be distinguished from the other parts of the rock by being partially penetrated 

 by Pholailes. 



t Plate XIV. fi-. 4. 



