Ch. XV.] OF THE PRIMARY ROCKS. 337 



We have also noticed a similar fact in the northern part 

 of Cornwall ; the strata are arranged in regular undulating 

 curves, but parallel with each other ; some are composed of 

 straight, others of curved and twisted laminae, exhibiting the 

 most intricate contortions. 



How can these facts be explained on the grounds of 

 mechanical violence ? for how is it possible that some strata 

 could be soft and others not, some bent and twisted, whilst 

 others give no indications of any forcible derangement : and 

 yet all these strata (if metamorphic) have been exposed to the 

 same igneous action, and all (whatever their nature) have 

 been subject to the same moving power, since they alternate 

 with each other in parallel beds ? This is no new objection ; 

 the same has been often urged by those who have contem- 

 plated the various anomalous arrangements of contorted 

 strata, arrangements which " cannot be explained by sup- 

 posing the beds to have been regularly deposited in the first 

 instance, and shifted afterwards by subsidences, shocks, or 

 convulsions." 



In addition to the anomalies above mentioned, it may be 

 stated that the contemporaneous quartz-veins (which sometimes 

 follow all the intricacies of the curved strata, and at others 

 traverse these curves in some places, and are parallel thereto, 

 in others, as if of a later origin) are occasionally found run- 

 ning a most serpentine and tortuous course through mica- 

 schist and other primary slates which are regularly arranged ; 

 for instance, at Tremearne, near Trewavas Head, in Cornwall, 

 in the vicinity of the junction of the slate and granite, the 

 former rock is traversed by quartz-veins under these circum- 

 stances ; and Macculloch has observed " that veins of quartz 

 sometimes occur in gneiss, which are most intricately con- 

 torted, although the laminae of the including rock show no 

 corresponding indications of flexure." And he adds, " this 

 is a difficulty which, among a thousand others, must remain 

 for future explanation ; and how far its solution may modify 



