282r Dr. Mac Culloch on the Junction 



in a clearer point of view. Where the red sandstones of the 

 west coast of Sutherland follow immediately on gneiss, the first 

 layer, as I have shown in my work on the Western Islands, is 

 an obscure conglomerate, consisting of gneiss, broken, and re- 

 united to the body of the rock. Such is the union, and such 

 generally the obscurity of the fragments, that it is often not 

 possible to determine where the gneiss terminates and the 

 conglomerate commences. A similar appearance and grada- 

 tion, where micaceous schist is followed by the sandstone, 

 occurs in Argyllshire. 



It is easy to understand that, under similar circumstances, 

 the fragments of a subjacent granite might form a compacted 

 conglomerate, not distinguishable from the original rock ; and 

 it is equally easy to see, that the alternation of layers of this 

 substance, with layers of argillaceous schist, derived from 

 some neighbouring source, would account for the extraordinary 

 appearances at this junction. 



The compactness of the whole, and its apparent identity with 

 the granite, are no further matters of surprise, than what takes 

 place in the cases above quoted, with respect to gneiss, or 

 micaceous schist ; since the lowest, their stratum of conglo- 

 merate, in these cases, appears to belong to the gneiss, or mica- 

 ceous schist, not to the superincumbent sandstone. 



With respect to the apparent transition between the granite 

 and the conglomerate which so much resembles it, I must 

 now also remark, that it is one of those resemblances which 

 so often deceive us with the appearance of identity. In the 

 work above quoted, I have mentioned instances in the red 

 sandstone of West Sutherland, and Ross-shire, where the finer 

 conglomerates, from the nature of their composition, and their 

 crystalline compactness, were scarcely distinguishable from 

 granite, on a superficial view. The same happens in the case 

 of quartz rock, so often, as to have deceived the observers of 

 this rock, and to have caused them to consider it akin to 

 granite. 



Yet, in these instances,, the nature of the rock, if it could 

 not be determined by mere inspection of the specimens, is 

 known by its connection and position ; no granite being pre-^ 

 Bent, and it being connected by a regular gradation, with un- 



