390 Appendix 
River to the Grand Wash, or about 600 from the Junction. From Green River 
Valley to the foot of Black Canyon something over 1000 would be a near estimate 
of the total number of rapids. The velocity is always tremendous. 
The width of the river varies according to the locality. Green River is from 
250 to 400 feet in the canyons, and 800 to 1000 in the valleys. The Colorado is 
from 75 to 400 or 500 in the canyons and from 1200 to 1500 in the valleys. In 
the Granite Gorges there are points where the distance between the buttresses at 
the water is no more than 50 feet. In Marble Canyon there are a dozen places 
where the width is not over 60 to 75 feet. The depth varies from several feet 
to an unknown quantity in the narrow parts. There is also a variation of depth 
with the year and the season. Years when the high mountains receive an abnor¬ 
mal snow-fall the river rises to abnormal heights and at such times the depth of 
water in the Grand Canyon is enormous and the velocity appalling. The 
current varies from three miles per hour to twenty or more. 
* After Dutton, Tertiary History^ p. 240. 
