38 TlMEHRl. 



a6tive and widespread ; and it may be that the absence 

 of fossils from the sedimentary formations is due to this 

 cause. The practical purposes to which the sandstone 

 and greenstone might be applied, such as building and 

 paving in the former case and road-making, for which 

 the latter is particularly adapted, are negatived by the 

 fa6l that the distance and the difficulty of transport 

 across the rapids of the rivers, would be out of all pro- 

 portion to the value of the rocks. Masses of ores of 

 iron, often of considerable size, and small quantities of 

 manganese ore, are found on, or are associated with, the 

 greenstone rocks. 



The metamorphic rocks include the various schists 

 (such as mica, hornblende, quartz, talc, and chlorite 

 schists), the nests and veins of quartz contained in these 

 schists, and gneiss, with which the schists are associated 

 in many localities, and of which a very large portion of 

 the colony is composed. The gneiss rests chiefly on 

 granite, and is often granitic, so much so that in small hand 

 specimens it would be almost impossible to determine the 

 difference; and in fewer cases it becomes even porphyritic. 

 Garnet crystals and quartz nests are very widely distri- 

 buted throughout this rock, and an impure graphite 

 (plumbago) has been found to occur in the Carabung and 

 the Barima rivers in the schistose rocks. The special 

 importance of these rocks, however, from an economic 

 standpoint, lies in the fact that gold is widely distributed 

 among them ; and more systematic search is gradually 

 bringing co light the still more interesting fact that it is 

 not only widely, but plentifully, distributed. 



The granitic rocks include quartz-porphyry and fel- 

 stone, and granite proper and syenite. The two former 



