National Geographic : 1970 Feb
Running two untamed rivers-the Middle Fork Salmon and the Salmon-the Craig heads passed through chasms full of the tu mult of roaring white water but serene with solitude and breathtaking scenery. As the party traveled on the Middle Fork, the river dropped 2,600 feet in 95 miles. The Salmon descends less steeply, but its boiling rapids are larger and rougher. For approx imately 180 miles the river cuts a gorge more than a mile deep. On snow-buried banks of the Salmon, Frank Craighead measures condensation nuclei in the atmosphere with a Gardner Small Particle Detector. Counts on the Salm on River, which averaged 1,000 particles per cubic centimeter, provide a comparative base for checking air pollution in cities, where counts may run 250 times as high. Sun strik ing the camera lens causes the optical flare. Wild Rivers Red lines mark sections of riversprotected or proposed for protection under the Wild and Scenic Rivers Act of 1968. The eight rivers 222 underlined are alreadypart of the system.