t 

 ARHAN. GEOLOGY. SECONDARY STRATA. 367 



bewildered with the recurrence of angles, substances, 

 and measurements, would rise from the perusal as unin- 

 formed as he would from a survey of the shore itself, 

 if he should examine it only as a cabinet of specimens. 

 The interest which it presents is of a more general na- 

 ture, and to comprehend that justly, it must be con- 

 templated in a very different mode. I shall therefore 

 begin by presenting the general notion as it was deduced 

 from the comparison of the minute portions, and shall 

 consequently describe it in the inverse order to that 

 of the examination from which the deductions were 

 made.* 



* I may here venture to suggest to the geologist who may visit 

 Arran, the mode which he should adopt in examining these strata. 

 This consists, conformably to the general plan, in commencing at the 

 lowermost stratum and following the series upwards. For this pur- 

 pose he must here begin at a central point, and thus pursuing the 

 elevated edges of the strata in both directions, he will more readily 

 discern their connexions than if he had traced them, either on their 

 flat surfaces, or by walking along the shore from one end to the other ; 

 in which case one half of the strata will meet him with their edges, 

 while the other will present their surfaces. 



As it is impossible to convey a clear notion of this subject without 

 diagrams,* I have added some ideal sections explanatory of the general 

 positions of the strata ; these will also save many repetitions and much 

 circumlocution. The different sections must be considered as deve- 

 loping the structure of a conoidal frustum with a concave superficies, 

 consisting of various laminae ; the irregularities being in one of them 

 reduced to the leading and elementary form. Their object, among 

 other things, is, to show the various inclinations of the strata on dif- 

 ferent parts of the shore, as the foundation of future reasonings. But 

 these are so irregular and unequal, that neither section nor enumeration 

 could render them thoroughly intelligible ; although a general notion 

 of this irregularity may be conveyed by a vertical section, which repre- 

 sents their varying curvature as they occupy either the flat shore or 

 the face of the hill, accommodating themselves to the forms of the 

 mountain against which they recline. I need scarcely add that no 

 attention has been paid to the quantity of the inclination, as such 

 details would have required numerous drawings. 



* Plate XXV. fig. 1, 2, 3, 4. 



