So, for a thousand generations on the Scottish hills, had Chum's ancestors earned their right to live. And so through successive generations had they imbued their progeny with that accomplishment until it had become a primal instinct. Even as the unbroken pointer of the best type knows by instinct the rudiments of his work in the field so will many a collie take up sheep herding by ancestral training.

There had been nothing wonderful in Chum's exploit. Hundreds of untrained collies have done the same thing on their first sight of sheep. The craving to chase and slay sheep is a mere perversion of this olden instinct; just as the disorderly "flushing" and scattering of bird coveys is a perversion of the pointer or setter instinct. Chum, luckily for himself and for his master's flock, chanced to run true to form in this matter of heredity, instead of inheriting his tendency in the form of a taste for sheep murder.

The first collie, back in prehistoric days, was the first dog with the wit to know his master's sheep apart from all other sheep. Perhaps that is the best, if least scientific, theory of the collie's origin.

But to Link Ferris's unsophisticated eyes the achievement was all but supernatural, and it doubled his love for the dog.

That afternoon, by way of experiment, Ferris took Chum along when he went to drive the sheep back from pasture to the fold. By the time he and the dog were within a hundred yards of the pasture gate Chum began to dance, from sheer anticipation; mincing sidewise on the tips of his toes in true collie fashion, and varying the dance by little rushes forward.

Link opened the crazy gate. Waiting for no further encouragement the dog sped into the broad field and among the grazing sheep that were distributed unevenly over the entire area of the lot.

Ordinarily—unless the sheep were ready to come home—it was a matter of ten or fifteen minutes each evening for Link to collect them and start them on their way. To-day, in less than three minutes, Chum had the whole flock herded and trotting through the opening, to the lane outside.

Nor, this time, did the sheep flee from him in the same panic dread as in the morning. They seemed to have learned—if indeed a sheep can ever learn anything—that Chum was their driver, not their enemy.

From the fold Link as usual went to the woodlot where his five head of lean milch cattle were at graze. Three of the cows were waiting at the bars for him, but one heifer and a new-dry Holstein were hidden somewhere in the recesses of the second-growth timber.

The afternoon was hot; it had been a hot day. Link was tired. He dreaded the labor of exploring ten acres of undergrowth for his two missing cattle. An inspiration came to him. Pointing to the three stolidly waiting cows at the bars he waved his arm in the general direction of the lot and called on Chum.