HYDROGRAPHIC REPORTS. 
In the establishment of a great inter-oceanic communication, 
like that projected across the Isthmus of Tehuantepec, the hy~ 
drographic results constitute an important element of success, 
and as full reports were made on this subject, I cannot do better 
than give the details in the language of those to whom this 
branch of the survey was confided. 
Extract from the Report of Mr. W. G. Temple, U. S. Navy, to 
Major J. G. Barnard, on the Survey of the Coatzacoalcos 
River. 
Under date of December 30th, 1850, I received from you the 
following instructions : 
" There are two principal objects in your survey of the River Coatzacoalcos : 
1st. To determine the proper head of sea navigation; 2d. To ascertain its 
capabilities for navigation by light-draught vessels as far up as Paso Sarabia. 
" As to the first point, it does not appear from the configuration of the river, 
that even if it is equally navigable, any point between Mina-titlan and the 
Island of Tacamichapa is preferable for the terminus to Mina-titlan itself, 
unless local circumstances, such as a peculiarly favorable site and a high ridge 
of land leading to it, should render it so. There is little doubt that the road 
will lie on the west or left side of the river, hence your exploration should be 
directed particularly to that. It is said that sea-vessels can ascend the Brazo 
Mistan as far as La Horqueta: should this be the case, the road would be 
materially shortened by selecting a terminus somewhere on this arm. It may 
be, however, that this branch, though deep, may be so narrow as to be unfit for 
sea-steamers, and be particularly difficult of passage for sailing vessels. Such 
considerations, of which you will judge, would decide the point in favor of 
Mina-titlan. You will, however, note all favorable sites within the limits of 
$m navigation. It is said that Almagres is high, and that a road could be run 
across the island to it. You will observe, therefore, whether the island appears 
to be above overflow, and whether this road, crossing the Brazo Mistan, would, 
train the east, approach the Brazo on favorable ground. To shorten the line 
materially, such a road should follow a line or lines as I have sketched on the 
map from Almagres. To terminate on the Mistan, it should follow the same 
