428 PROCEEDINGS Of THE GEOLOGICAL SOCIETY. [May 24, 



is very shallow by the accumulation of this ferruginous gravel. At 

 the base of Mecropie hill the same occurs. 



Derrire hill is covered with hydro-oxide of iron ; and much of it has 

 been brought down, in the form of gravel, into the creek bearing the 

 same name. 



At Camoodecabra a trap rock rises, and extends to the Anobaro 

 Creek, forming a dangerous barrier for boats descending the river. 

 Above the "Waburicabra another large ferruginous gravel-bank occurs 

 that extends up almost as far as Coomaparo creek. 



From Coomaparo there is an Indian path to the Essequebo river, 

 which occupied eight hours' walking. The land rises in undulating 

 swells up to the " burnt grounds," where it attains 200 feet, and, 

 after continuing on that level for a few miles, gradually descends, 

 like steps, until it reaches the low swampy flat of Moraboo, on the 

 east bank of the Essequebo. 



In this distance, computed at 18 miles, the only rock to be seen is 

 a quartzite, which decomposes into white sand. 



Eeturning to the Demerara river, the banks continue low untU 

 arriving at Acururi Hill, which connects with a ridge that extends to 

 Lucananycabra, chiefly composed of white sand. 



By proceeding up the Marbooroo creek about a mile, and then 

 walking south-west a few miles, the Maburu Hill rises to about 

 800 feet above the sea : one of its sides towards the Essequebo is 

 nearly perpendicular; and from it a fine view of that river is 

 obtained. It is composed of trap, and appears connected with the 

 same range that forms the dyke at the great falls of MalaUi. 



The falls of MalaUi are 35 feet in perpendicular height, and form 

 the greatest barrier to the navigation of the Demerara river. 



At the base of the falls may be seen ejections of trap and por- 

 phyry between the granite ; and on the confines of the basin below 

 the falls, several interesting examples of weathering and decom- 

 position of the granite. 



The trap or greenstone, that has passed up the fissures or lines 

 of weakness, appears very dense, and so fine-grained that it might 

 be taken for petrosUex. The curious contortions and the splitting 

 of veins that have forced their way through masses of granite are 

 exceedingly interesting and instructive. 



The hornblendic rocks continue over a distance of ten miles up 

 the river, occasionally rising to the surface, but more frequently 

 observed covered by clays and sands, resulting from the decompo- 

 sition of these and granitic rocks. 



"Where the clays or sands form the banks of the river the land is 

 low and often swampy for miles around, intersected by numerous 

 bayous, showing a considerable depression of the country. 



On approaching Navaroo creek, granite occurs of a very beautiful 

 character, with purplish felspar and green mica. 



There are several large boulders near Kanimapoo's Landing, 

 This series of granite continues up the river four or five miles. A 

 very good yellow-ochre appears to be the result of its decomposition, 

 and occurs in thick beds in this vicinity. 



