At six months it was discovered that he was a natural watch-dog. Also that he never barked except to give an alarm. A collie is, perhaps, the most excitable of all large dogs. The veriest trifle will set him off into a thunderous paroxysm of barking. But Wolf, the Boy noted, never barked without strong cause. He had the rare genius for guarding that so few of his breed possess. For not one dog in ten merits the title of watch-dog. The duties that should go with that office are far more than the mere clamorous announcement of a stranger's approach, or even the attacking of such a stranger. The born watch-dog patrols his beat once in so often during the night. At all times he must sleep with one ear and one eye alert. By day or by night he must discriminate between the visitor whose presence is permitted and the trespasser whose presence is not. He must know what class of undesirable to scare off with a growl and what class needs stronger measures. He must also know to the inch the boundaries of his own master's land. Few of these things can be taught; all of them must be instinctive. Wolf had been born with them. Most dogs are not. His value as a watch-dog gave Wolf a settled position of his own on The Place. Lad was growing old and a little deaf. He slept, at night, under the piano in the music-room. Bruce was worth too much money to be left at large in the night time for any clever dog-thief to steal. So he slept in the study. Rex, a huge mongrel, was tied up at night, at the lodge, a furlong away. Thus Wolf alone was left on guard at the house. The piazza was his sentry-box. From this shelter he was wont to set forth three or four times a night, in all sorts of weather, to make his rounds. The Place covered twenty-five acres. It ran from the high-road, a furlong above the house, down to the lake that bordered it on two sides. On the third side was the forest. Boating-parties, late at night, had a pleasant way of trying to raid the lakeside apple-orchard. Tramps now and then strayed down the drive from the main road. Prowlers, crossing the woods, sometimes sought to use The Place's sloping lawn as a short cut to the turnpike below the falls. For each and all of these intruders Wolf had an ever-ready welcome. A whirl of madly pattering feet through the dark, a snarling growl far down in the throat, a furry shape catapulting into the air--and the trespasser had his choice between a scurrying retreat or a double set of white fangs in the easiest-reached part of his anatomy. The Boy was inordinately proud of his pet's watchdog prowess. He was prouder yet of Wolf's almost incredible sharpness of intelligence, his quickness to learn, his knowledge of word meaning, his zest for romping, his perfect obedience, the tricks he had taught himself without human tutelage--in short, all the things that were a sign of the brain he had inherited from Lad.