REPORT AND ESTIMATE. 343 
obliquely. A single arch will always be sufficient. It will sometimes be necessary to resort 
to side walls. The trail crosses the river forty-four times. The number of bridges” will be 
much less; several tributary streams to be bridged; much culvert work; road-bed to be well 
raised. The valley is not subject to overflow; its banks are four to twelve feet above water- 
level, several places covered with water at its highest stage. Greatest rise and fall near the 
mouth of the St. Regis de Borgia, about five and a half feet; sixteen miles higher up, four feet. 
There will be considerable wood to cut through, and much gravelling. The wood will generally 
be a small growth in the river bottoms. The materials for construction will be literally 
inexhaustible. Good limestone was observed at several points, especially about midway of the 
section. 
TUNNEL AT STEVENS'S PASS OF THE CŒUR D'ALÉNE MOUNTAINS. 
This tunnel will be 1} miles, in easily worked limestone and earth. It passes from the Coeur 
d' Aléne to the St. Regis de Borgia in a south by east course, making nearly a right angle with 
the general course of the road. The summit is at the eastern debouche, at an elevation of 
3,990.03 feet above the sea. It descends to the west at a gradient of sixty feet to the mile, and 
its elevation on the western extremity is 3,811. 1 feet above the sea. The summit level of the 
divide on the usually travelled trail is 5,089.7 feet. 
TUNNEL TO CŒUR D'ALENE MISSION—DISTANCE 48} MILES. 
In this distance the line falls 1,586.9 feet to an elevation of 2,290.8 feet above the sea, and 
giving an average gradient of 32.74 feet to the mile. The grades along the immediate valley of 
the river are as follows: 
ith mile, 94.8 feet to the mile. | 
loca INES cigs do. 
3---49-:181.8...... do. 
}..-do--181.4-+++--do. 
і...4о.. £53. do. 
1....do-. 19.2.-.... do. 
8...do.- 668 do. 
31...do.. 56.1...... do. 
Ness doe» 28. 1 d0 
6 do-- 60.6...... do А 
5 до. . 38.34. .... do r 
8 do 117..... do 
11 do 3.6 do 
481 miles, fall 1,586.9, grade 32.74 feet to the mile. 
For the first 102 miles from the tunnel the road must be very carefully located along the 
side hills, north of the river, to use sixty feet gradients. The side hills run gently to the river. 
There is a narrow open valley for 25 miles to the point where the trail crosses the river to pass 
over the divide, and for 43 miles further the route is through wood, sometimes of small growth. 
In this distance three streams are crossed. The next nine miles will require там ome in 
location. The trail passes over low side hills north of the river, and in some cases a mile from 
