goode.] MONUMENTS. 
Boundary Commission engaged in the survey and re-marking of the 
boundary between the United States and Mexico west of the 
Grande; and as the conclusions reached so nearly correspond to those 
arrived at in connection with the Idaho-Montana line, the folio* 
quotations are made : 
The method by stadia is cheap and rapid; requires less cutting than thai by chain; 
is carried on under the eye of an instrument man, presumably of a high ordi 
intelligence; gives heights and angles, and enables objects to be located from the 
line which is being measured; is ordinarily more accurate than the chain, and 
can be successfully used where the chain can not be, experience on this survey 
having shown that the stadia lines over mountains, hills, and canyons were more 
accurate than those on level plains and wide valleys. * * * 
In view of this proof of the inevitable change in the value of the interval, the 
common practice of painting a rod to correspond with the stadia into n a of a cer- 
tain hour and day and then continuing the use of such rod unchecked and 
unchanged during the widely different seasons of this country oftentimes— in 
fact, for many years at a time— is seen to be inviting the large systematic error 
which almost without exception characterizes such work. If this evidence be 
taken to prove the fact that even so-called fixed stadia wires actually change their 
relative positions, or, whatamountsto the same thing, appear to change on accounl 
of the influence of differential refraction at different seasons, then fch< 
method of painting the rod to correspond with the determined interval is oh 
tionable because of the cost of regraduating and repainting the rod to correspond 
to such change in interval. A method entirely free from this objection of cost, 
and one which the writer has found to stand every test during several years of 
field use, is that which uses rods divided into true units of feet, yards, or meters 
and employs an interval factor in the computation of distances. With tl 
a change in the interval simply means the loss of an hour's time in the preparati< m 
of a new table for reduced or true distances corresponding to any rod reading. 
MONUMENTS. 
The monuments used along the meridional portion of the Line are 
of two kinds — stone and iron. The stone monuments are of granite, 
6 feet in length and 10 inches square, undressed excepl for spaces 
sufficient to permit cutting the words "Idaho" and " Montana," on 
opposite sides. These monuments are placed in the more prominent 
localities, and are monolithic in all cases Where LI was possible to 
transport them in one mass to the proper position; otherwise thej 
were cut into ten sections, so that they could be carried on pack 
mules, and were bolted and cemented together when established Ln 
place? The monuments at the international boundary and at the 
summit of the Bitterroot Mountains, these being the terminal points 
of the meridional portion of the line, are of si <»ne made from sections, 
as described, and monoliths are placed near tin- points al which 
boundary line crosses the Northern Pacific and Great Northern rail- 
ways. (See PL VII.) The iron monuments are hollo* posts of 
wrought iron, 6 feet in length and about 1 inches in outer diameter, 
covered with a coat of asphaltuni tar. At the bottom they are flared 
