After lunch Bob wandered out into the dazzling sunlight.  The sky was wonderfully blue, the trees softly green, the new boards and the tiny pile of sawdust vividly yellow.  These primary colours made all the world.  The air breathed crisp and bracing, with just a dash of cold in the nostrils that contrasted paradoxically with the warm balminess of the sunlight.  It was as though these two opposed qualities, warmth and cold, were here held suspended in the same medium and at the same time.  Birds flashed like spangles against the blue.  Others sang and darted and scratched and chirped everywhere.  Tiny chipmunks no bigger than half-grown rats scampered fearlessly about.  What Bob took for larger chipmunks—­the Douglas Squirrels—­perched on the new fence posts.  The world seemed alive—­alive through its creatures, through the solemn, uplifting vitality of its forests, through the sprouting, budding spring growths just bursting into green, through the wine-draught of its very air, through the hurrying, busy preoccupied murmur of its streams.  Bob breathed his lungs full again and again, and tingled from head to foot.

“How high are we here?” he called to Welton.

“About six thousand.  Why?  Getting short-winded?”

“I could run ten miles,” replied Bob.  “Come on.  I’m going to look at the stream.”

“Not at a run,” protested Welton.  “No, sir!  At a nice, middle-aged, dignified, fat walk!”

They sauntered down the length of the trestle, with its miniature steel tracks, to where the flume began.  It proved to be a very solidly built V-trough, alongside which ran a footboard.  Welton pointed to the telephone wire that paralleled it.

“When we get going,” said he, “we just turn the stream in here, clamp our sawn lumber into bundles of the right size, and ‘let her went!’ There’ll be three stations along the line, connected by ’phone, to see that things go all right.  That flume’s six mile long.”

Bob strode to the gate, and after some heaving and hauling succeeded in throwing water into the flume.

“I wanted to see her go,” he explained.

“Now if you want some real fun,” said Welton, gazing after the foaming advance wave as it ripped its way down the chute.  “You make you a sort of three-cornered boat just to fit the angle of the flume; and then you lie down in it and go to Sycamore Flats, in about six minutes more or less.”

“You mean to say that’s done?” cried Bob.

“Often.  It only means knocking together a plank or so.”

“Doesn’t the lumber ever jump the flume?”

“Once in a great while.”

“Suppose the boat should do it?”

“Then,” said Welton drily, “it’s probable you’d have to begin learning to tune a harp.”

“Not for mine,” said Bob with fervour.  “Any time I yearn for Sycamore Flats real hard, I’ll go by hand.”

He shut off the water, and the two walked a little farther to a bold point that pressed itself beyond the trees.