ORIGIN AND DEVELOPMENT OF OKE-DEPOSITS. 287 



is scarcely to be doubted that sensible earth-movements are still 

 taking place in many parts of our mining districts, and in this 

 connexion it is interesting to note that according to Professor 

 Milne and other observers, a movement of a quarter of an inch 

 is quite sufficient to produce such earthquake shocks as are 

 commonly observed in the West of England and in Wales. Every 

 such movement must occasion an earthquake, or at least an 

 earth-tremor, and it is well-known that few years pass without 

 such movements being experienced in the West of England. 

 The enormous local pressures sometimes experienced underground 

 are also probably due to similar local earth-movements. 



Class XIV. — Newer Flucans and Slides. 



" Slides may be defined as fault fissures containing clay 

 and having a great underlie " {i.e. — a low inclination from the 

 horizontal) ; flucans as similar fissures having a moderate 

 underlie.* 



Slides and flucans traverse and usually displace all the 

 metalliferous veins as well as the spar veins or stony cross- 

 courses of a district. Their bearings are very frequently near 

 to those of the various metalliferous veins of their respective 

 districts whether "Champions," " Caunters," or "North and 

 South lodes. "f They are no doubt in some instances, at least, 

 very ancient as compared with the faults which I have called 

 " Alluvial," but as they rarely contain either metallic ores 

 (except sometimes oxide of iron) or quartz, and as they cut 

 through every kind of metalliferous vein, it is probable that 

 they have been formed since the circulation of metalliferous 

 solutions has practically ceased. According to Mr. Hen wood J 



* In some parts of the district, the terms flucan and slide are applied 

 indiscriminately to all veins which are composed mainly of clay, in others only 

 clay veins of low underlie whose bearing is nearly that of the lodes, are called 

 slides, all other clay veins being called flucans ; but more usually the terms are 

 used as stated above. In this paper the term slide is applied only to clay veins 

 whose inclination from the horizontal is less than 25°, all other clay veins being 

 called flucans. 



fChampion or right-running lodes have their bearings within 25° or 30° of 

 that of the main axis of Cornwall, which is very nearly magnetic E.W. Lodes 

 bearing within 20° or 30° on either side of th.e magnetic meridian, are known as 

 North and South lodes. Those whose bearings are intermediate are known as 

 Gaunter or " Contra " lodes. 



X Met. Dep., Trans. Eoy. Geol. Soc. Corn., Vol. V, 282. 



