50 
EN G I NEEK fNG REP GETS . 
These were occupied mainly in transporting baggage, provi- 
sions, &c, and in cutting paths through the woods to expedite 
our operations : in this latter business they were very expert, 
using their machetes with great dexterity and effect. 
In order that you may be able to judge of the degree of con- 
fidence that may be placed in the results given, I deem it im- 
portant to state, that on commencing operations in the field, it 
was strictly enjoined on each member of the party to use the 
utmost care in obtaining accurate results in every part of the 
work; and we have availed ourselves of every means in our 
power to guard against errors. The line on which the estimates 
were based, was traced for the entire distance with a transit by 
means of backsights, the magnetic bearing being noted at every 
change as a test of the correctness of the deflections. We find 
on working out the courses of the line, by the deflections as 
actually measured in the field, that the total error in the distance 
of forty-one miles amounts to but one degree and thirty minutes, 
the most of which occurs in the last four or five miles run ; so 
that by making the slight correction indicated by the needle, 
the line may be considered practically perfect. 
About ten miles of the line, including the roughest portions, 
were accurately cross-sectioned with a spirit-level, and the to- 
pography carefully sketched for the entire distance ; the char- 
acter of material to be excavated, as well as could be judged 
from surface indications, was also noted. In running the levels, 
the readings of the rod at every change were recorded by the 
rod-man, independent of the leveller, so as to guard against the 
possibility of error. In our estimates of the amount of material 
to be moved in the construction of the road, we have taken into 
account the cross-section of the ground, wherever it was suffi- 
ciently sloping to essentially vary the result ; and in determin- 
ing the amount of water-way necessary to pass the streams in- 
tersecting the line of road, we have allowed about double the 
space that would be deemed necessary for streams draining 
the same area of country in the United States. 
For the entire distance from the Jaltepec River to the plains 
of Xochiapa, the line of survey crosses but two streams which do 
not offer a sufficiently good foundation to build upon, without 
