370 ARIIAX. GEOLOGY. SECONDARY STRATA. 



other, those which lie above the lowest bed on each 

 hand; to trace their identity if such exists, or else to 

 decide upon their independent and partial nature. It 

 is from this foundation also that we must attempt 

 to conjecture the mass and depth of the strata, 

 the measurement of which must be derived from the 

 lowest point of that foundation. Without it the whole 

 of them present but a dubious and confused repetition 

 of similar rocks, with little interest and a very uncertain 

 connexion. 



The conglomerate which forms the greatest portion 

 of the fundamental mass, is similar to that which accom- 

 panies the red sandstone in other situations, in Scotland 

 as well as elsewhere. It is an aggregate of quartz sand 

 and red ochrey clay, with a little mica; together with 

 rounded pebbles and angular masses of different sizes, 

 often attaining a very great magnitude. These consist 

 of clay slate, micaceous schist, graywacke slate, quartz, 

 and pieces of former sandstones. Such at least are the 

 prevalent ingredients ; if it contains fragments of other 

 rocks, as is possible, they are neither numerous nor con- 

 spicuous ; and I must add, that in no instance did I dis- 

 cover a fragment of granite in it. This conglomerate, 

 although apparently the basis of the strata on each side, 

 is not, strictly speaking, the lowest rock ; as there is 

 found under it a bed of red sandstone with white stains, 

 similar to that which will hereafter be described, accom- 

 panied by a bed of limestone remarkable for contain- 

 ing rounded and angular fragments of quartz ; a con- 

 glomerate which occurs in other parts of the series 

 that follows. Nothing lower than this is to be seen, 

 nor is there any ground for conjecturing what strata 

 may still lie between it and the schist in this place ; 

 since, as will readily be inferred after the mass of strata 

 has been described, the contact of the schist with a 

 given bed in one place, is no criterion of its relative 

 position in any other. In proceeding northward from 



