He fumbled with mittened fist at the cover of the directional radiation compass strapped to his left wrist. The outer dial rotated as soon as the cover lock was released and came to a stop pointing to magnetic north. The detector needle quartered across the northeast quadrant of the dial like a hunting dog and then came to rest at nineteen degrees, just slightly to the left of the direction of their tracks. An inner dial needle quivered between the yellow and red face of the intensity meter. "We should be within a couple of hundred yards of the marker now," Troy announced as his short, chunky partner checked alongside. Alec nodded and peered through the curtain of sky-darkened snow just beyond the rock face. He could see powder spume whipping off the ridge crest twenty feet above them but the contour of the sloping ridge was quickly lost in the falling snow. [Illustration] The hydrologists leaned on their ski poles and rested for a few minutes before tackling the final cold leg of their climb. Each carried a light, cold-resistance plastic ruckpac slung over their chemically-heated light-weight ski suits. A mile and a half below in the dense timber, their two Sno cars were parked in the shelter of a flattened and fallen spruce and they had thrown up a quick lean-to of broken boughs to give the vehicles even more protection from the storm. From there to the top, Troy was right in his analysis of DivAg. When God made mountain slopes too steep and timber too thick, it was a man and not a machine that had to do the job on skis; just as snow surveyors had done a century before when the old Soil Conservation Service pioneered the new science of snow hydrology. The science had come a long way in the century from the days when teams of surveyors poked a hollow, calibrated aluminum tube into the snow pack and then read depth and weighed both tube and contents to determine moisture factors. Those old-timers fought blizzards and avalanches from November through March in the bleak, towering peaks of the Northwest to the weathered crags of the Appalachians, measuring thousands of predesignated snow courses the last week of each winter month. Upon those readings had been based the crude, wide-margin streamflow forecasts for the coming year. Now, a score of refined instruments did the same job automatically at hundreds of thousands of almost-inaccessible locations throughout the northern hemisphere. Or at least, almost automatically. Twenty feet above the two DivAg hydrologists and less than a hundred yards east, on the very crest of an unnamed peak in the wilderness of Idaho's Sawtooth Mountains, radiation snow gauge P11902-87 had quit sending data three days ago.