238 Dr. MacCulloch on the Distribution of Granite 



the primary strata is not the one at the surface. Nor does 

 the general outline afford the least assistance, as the same con- 

 tinuous and low undulating line often pervades both classes of 

 rock alike. Thus, the geological surveyor must every where 

 intersect, in the minutest manner, the ground which he is ex- 

 amining; nor is it till after many successive trials, and much 

 minute observation, that he is enabled to trace the boundaries- 

 of the several rocks as they appear at the surface. This, 

 however, is a necessary part of his duty. It is to little pur- 

 pose, whether for the objects of science or economy, to con- 

 struct a map in which, instead of observations correctly lo- 

 calized, general features are expressed. Nothing useful can 

 be drawn from a survey of this nature, while the practice is 

 attended with the further evil of encouraging a hasty mode of 

 concluding, instead of examining ; and thus of substituting 

 prejudices for facts, and fiction for truth. 



The difficulties which attend the examination and discovery 

 of small tracts of granite are, however, very much augment- 

 ed, where it occurs in independent situations, and in a scat- 

 tered manner, in districts of primary strata, where no exten- 

 sive masses of it are present. Here it is impossible to con- 

 jecture where it is to be found, or where, after being once 

 found, it is again to be expected. In these tracts it occurs in- 

 differently in the lowest and in the highest situations ; nor is 

 it in general marked by any peculiarity of outline, or by any 

 one circumstance indicating its existence. The observer only 

 finds it at his feet, and cannot even always recognise it as cer- 

 tain, till he has detached a specimen. Thus, if he is desirous 

 to gain a reputation for accuracy, or really to lay down the 

 rocks that occur in any given district, he dares not omit even 

 a square mile in his investigation, or even, in many cases, far 

 less ; but is obliged to traverse every spot where this rock, 

 giving no data from which to infer its existence, may be found. 

 It is, indeed, from the number of any such smaller masses of 

 rock, whether of granite or others, found in any geological 

 survey, that the accuracy of the observer may be conjectured. 

 General details are in every one's power, but of such it may 

 truly be said, in the ancient maxim, that " dolus est generali- 



