General Geoloyy. 29 



traversed by low rolling ridges, while the foliated varieties of the 

 acidic gneiss give rise to relatively low-lying plains. But the more 

 basic members, such as the hornblende-schists, epidiorites and amphi- 

 bolites, usually j^i'oject from the gneissose plains, and give rise to 

 elevations varying from low knobs to ranges of hills which, as, for 

 example, the Blue Mountains in the lower Essequibo district, may 

 attain to heights of several hundred feet. 



The strike of the foliation of the gneiss varies greatly in direction, 

 and in the districts I have visited its trend varies in all directions even 

 over comparatively small ai'eas — it may be, in places, north and south, 

 whilst it may be in others in the near vicinity east and west. 



This complexity of foliation^ — ^due probably to recurrent earth-stresses 

 acting in diflerent directions and with varying intensities — was noticed 

 and recorded by C. B. Brown. 



The general geological structure of the colony in the districts not 

 covered by the sandstone formation resembles to a marked degree 

 that of the north-eastern sealjoard of North America, and of the 

 Brazilian seaboard of South America, north of Rio Janeiro. 



