"If we could only have gotten on the trail of the rascals sooner, Bud, we might have learned the secret," spoke Nort. "We ought to keep better watch!" "How could we?" asked Bud. "We shoot off on the trail, now, as soon as we hear of anything." "Yes, but we ought to get on the jump quicker," insisted his cousin. "If we had an airship, for instance!" and he laughed at the impracticability of his remark. "You can see pretty nearly the whole of the valley from the top of Snake Mountain," spoke Dick, when he and Bud had joined in the laugh at Nort's airship idea. "If one of us could be up there--" "We'd have to be there all the while!" interrupted Bud. "There's no telling when the rustlers will come. Talk about being on the watch! It's all right to say so, but how you going to work it?" Dick suddenly uttered an exclamation. "What's the matter?" his brother wanted to know. "See a snake?" "No, but I've got the idea! A watch tower! Why not build one at our camp--or up on the side of the hill back of the reservoir? We could make it of logs--high enough to give us a good view. It wouldn't be much of a trick to climb up in the watch tower three or four times a day and survey the place. A watch tower is the thing, Bud!" CHAPTER XII IN SPITE OF ALL Nort and Bud stared at Dick for several seconds without making any remark. They were sitting on their ponies, completely baffled by the manner in which the trail of the rustlers had suddenly "petered out." And they had been about to turn and go back to camp when Dick made his enthusiastic remark. "A watch tower?" repeated Bud. "Sure!" declared his cousin. "We used to build 'em when I belonged to the Boy Scouts. Remember, Nort?" "Sure! It begins to come back to me. We used to bind saplings together and make quite a high perch. The idea was that you might be able to see your way if you got lost," he explained to Bud. "Not a bad idea, either," commented the western lad. "I begin to see your drift, as the wind said to the snowstorm. You mean to build a sort of high platform up by the reservoir, Dick?" "Yes, a watch tower of logs, strong enough to hold one or two fellows. You could make ladders so's we could reach the top platform, or we could scramble up if we left hand and foot holds where we lopped the branches off saplings." "That's right!" cried Bud, now almost as enthusiastic as was his cousin. "And with a good pair of glasses, or a telescope such as dad has at the ranch, we could see all over the valley." "Let's make it!" cried Nort, and the matter was settled as quickly as that. Something of the excitement that had moved them must have been visible on the faces of the boys when they returned to camp, for Old Billee, greeting them in the absence of the other cowboys, asked: "Did you land 'em, Bud?" "Who; the rustlers? No. Couldn't see where they'd vanished to any more than, as one of the boys said, as if an airship had been used. But we got an idea, Billee."