ENGINEERING EEPOETS. 
41 
of iron. This rock will furnish abundance of excellent building 
stone, and also a valuable gritstone for purposes of grinding and 
polishing. 
In following up the valley of the Malatengo, the direction of the 
line of survey necessarily coincides very nearly with the course 
of the river : for about one half this distance the road will have 
a very good alignment, but for two or three miles there is con- 
siderable curvature, the minimum radius being one thousand feet. 
In order to secure as good an alignment as possible, we are 
obliged to make four crossings of the river, requiring one 
bridge of 125 feet span, one of 150 feet, and two of 175. The 
elevation of the abutments will vary from 35 to 50 feet, and 
will rest on solid rock. All the stone required for their masonry 
can be obtained from the excavations, or may be quarried 
within a few feet of the work. There will also be required a 
bridge of 50 feet span at the crossing of the Xuchiapa Creek. 
Commencing at the confluence of the above creek, the bed of 
the Malatengo breaks down suddenly, forming a succession of 
falls and rapids for a distance of two miles ; the greatest fall in 
one mile being 90 feet, and the total for two consecutive miles, 
141 feet. The maximum grade on this part of the route is 60 
feet per mile, and the greatest elevation of the grade-line 
above the bed of the river 55 feet. The extreme rise of water 
in the channel of the river is from 15 to 20 feet, depending 
upon the width of the channel and the rapidity of the current. 
The banks of the stream are sparsely covered with a growth of 
trees and underbrush, embracing three or four varieties of tim- 
ber of good quality, and in sufficient quantity to answer all 
purposes of construction. 
We found the survey of this portion of the route very labo- 
rious, owing to the precipitous nature of the ground. After 
running a base-line through, accurate cross-sections were taken 
at intervals of 100 feet, and for the entire width to be occu- 
pied by the road; by which means we are enabled to make 
a very close estimate of the amount of work required in its 
construction. The cost will here be somewhat increased by 
the difficulty of getting to and from the work. There can, how- 
ever, be a good mule-road opened along the immediate banks 
