Surveying and Mapping British Guiana. 57 
The greater part of the country, as already stated, is covered with thick 
forest, and triangulation is not practicable except in the western part of the 
hinterland. The method to be adopted, as pointed out by Major J. M. Gordon, 
in his memorandum dated 4th December, 1911, to the Right Honourable the 
Secretary of State for the Colonies dealing with an Estimate of the cost of 
a survey of the portion of the Colony lying north of latitude 4° N., 
and published in Combined Court Sessional Paper No. 638 of 1912, would 
be to run traverses up all the main rivers and to connect. them by cross 
traverses through the forest, and to check the whole work by numerous 
astronomical observations. 
In order to reduce the cost of cutting ana chaining lines along the banks of 
the rivers for the main traverses, the Subtense method could with advan- 
tage be adopted wherever the nature of the streams admitted. The angles 
of these traverses would require to be carefully observed and checked fre- 
quently by azimuth observations. 
Permanent marks with, if possible, a distinguishing number, should be 
erected at, say, every 5 miles along the main river traverses to serve as bea- 
cons for tying on other survey work which might be done in future years. 
The portion of the boundary between Brazil and British Guiana and which 
is laid down by Treaty as “ the watershed line between the Amazon Basin and 
“the Basins of the Courantyne and the Essequibo from the source of the 
“ Courantyne to that of the Takutu ’ would have to be surveyed before the 
extreme southerly limits of the colony can be definitely ascertained. This 
boundary approximately 400 miles in length, would probably require to be 
done in conjunction with representatives of the Brazilian Government, and 
on account of the nature of the country and its distance from Georgetown 
as the base of supplies, necessarily cost more money per mile than the other 
traverses. 
In the attached lists 1 give (a) the estimated mileage of the main rivers to 
be traversed, and the connecting lines across country to be cut and 
traversed; (b) the estimated mileage of the tributary streams to be 
surveyed, if possible by Compass and Float Line ; which I think would 
have to be done to provide the data for making the frame-work map 
T suggest. 
This work summarised is as follows :— 
Miles. 
(1) River Traverses the se ae 5,350 
(2) Traverses of connecting lines across country he bis 950 
(3) Traverse of South Boundary .. ad 400 
4) Surveys of Tributary Streams by Compass and Float Line, 
where practicable aa its Shs sis * 6,700 
Yo form an accurate estimate of the cost of executing this field work is by 
no means an easy task, and it is with considerable diffidence that I approach 
this aspect of the matter, 
