ENGINEERING REPORTS. 
51 
the necessity of reversed arches, or other artificial support. In 
a majority of cases the foundations of bridge and culvert ma- 
sonry will rest on solid rock. By reference to the maps, it will 
be seen that the alignment is remarkably favorable, with the 
exception of a short distance through the valley of the Mala- 
tengo, and even there the minimum radius of curvature is 
greater than on many of the principal roads in the United 
States. 
It will also be seen, by the profile, that for a great por- 
tion of the distance, we encountered a succession of cuts and 
fills, which, though amounting to a considerable quantity 
in the aggregate, do not give very heavy work at any one 
point. This should be considered a favorable feature in the 
route, inasmuch as the opportunity thus afforded for the divi- 
sion of labor will greatly facilitate the early completion of the 
road. 
We completed our surveys to the south of the Jaltepec River 
on the 25th of May, and arrived at Mina-titlan on the 28th. 
Being detained here a few clays, awaiting the arrival of the 
parties from the southern division of the Isthmus, we improved 
the time in running a compass line from Mina-titlan to the 
Hacienda of Almagro, where it joined the line through from the 
Jaltepec, thus making a connected instrumental survey from 
Mina-titlan to the bay of Yentosa. This line being accurately 
traced with a compass and chain, afforded us a good base from 
which to determine a number of important points by triangula- 
tion. "We used for this purpose the distances between Cosu- 
liacaque and Jaltipan, and also between the latter place and 
Tesistepec, from each of which points we had an extensive 
view of the country in all directions. 
While a portion of the party were engaged as above, Messrs. 
Murphy, Smith, and myself made a reconnaissance of the 
country to the east of the Coatzacoalcos, bordering the Uspanapa 
and Tancochapa rivers with a view of obtaining sufficient data 
to enable us to map correctly a portion of the Isthmus that was 
previously but little known. Taking with us a transit, we pro- 
ceeded directly to the Hacienda of San Jose del Carmen, situ- 
ated on the west bank of the Tancochapa River, 20 miles from 
