16 SURVEY OF IDAHO-MONTANA BOUNDARY LINE. [bull. 170. 
was reduced 140,080 square miles by the formation of the Territory 
of Montana, which was taken entirely from Idaho, and in 1868 it was 
further reduced by the formation of the Territory of Wyoming, almost 
the whole of which (93,995 square miles) was taken from Idaho. Mon- 
tana to-day stands as originally organized, while Idaho contains about 
84,800 square miles. 
The present boundaries of Montana are described as follows : 
Beginning at the intersection of the twenty-seventh meridian of longitude with 
the boundary line between the United States and the British possessions, it fol- 
lows said meridian south to the forty- fifth parallel of latitude; thence west on this 
parallel to the thirty- fourth meridian; south on the thirty- fourth meridian to the 
point where that meridian intersects the continental watershed; thence westward 
and northwestward, following the line of the continental watershed and the sum- 
mit of the Bitterroot Range to its intersection with the thirty-ninth meridian; 
thence north on the thirty-ninth meridian to the boundary line between the United 
States and British possessions, and east on that boundary line to the point of begin- 
ning. 
The present boundaries of Idaho are described as follows : 
Beginning at the intersection of the thirty-ninth meridian with the boundary 
line between the United States and the British possessions it follows said meridian 
south until it reaches the summit of the Bitterroot Mountains; thence southeast- 
ward along the crest of the Bitterroot Range and the Continental Divide until it 
intersects the meridian of thirty- four degrees of longitude; thence southward on 
this meridian to the forty-second parallel of latitude; thence west on this parallel 
of latitude to its intersection with a meridian drawn through the mouth of the 
Owyhee River; north on this meridian to the mouth of the Owyhee River; thence 
down the midchannel of the Snake River to the mouth of the Clearwater; and 
thence north on the meridian which passes through the mouth of the Clearwater 
to the boundary line between the United States and the British possessions, and 
east on said boundary line to the place of beginning. 
The boundary under discussion is the common one mentioned 
above. 
In the United States State boundary lines may be grouped in two 
general classes : 
First. Those that are defined by some natural physical feature, 
such as an ocean or a lake shore, the channel or bank of a stream, the 
summit of a range of mountains, or a watershed. 
Second. Those that are defined by imaginary lines which must be 
traced on the earth's surface by astronomic or mathematical processes. 
Such a line may be a meridian of longitude, a parallel of latitude, a line 
between two points (such as a portion of the eastern boundary of 
Nevada, which is from the intersection of the one hundred and twen- 
tieth meridian and the thirty-ninth degree of latitude to a point on 
the Colorado River where it intersects the thirty-fifth degree of lati- 
tude), a line defined by azimuth and distance or a number of such 
lines consecutively joined (such as the boundary line between Maine 
and New Hampshire), a line determined by a given direction from a 
certain point terminating at its intersection with some other line 
