David did not like being called down before all the others and he could hardly keep from expressing his feelings in a forcible manner. But upon second thought he suppressed the impulse. Perhaps the man was trying to pick a fight. “What’s the reason for it?” he asked. “Why did the milk get hard like that?” “Dirt, of course. You’ve been using the same old cups every day when you should make new ones at least every third day.” “What do you want done with this? Isn’t it worth anything?” David asked. “Throw it into the scrap heap. The boss is entitled to all the rubber on his property, and if anyone wastes it, as you have done, he suffers a loss. But I’ll see that he doesn’t lose anything in this case. I’ll charge it against your work,” the foreman said in an angry manner. That part did not trouble David greatly. He was not counting so much on earning money as on winning the good will of everyone around him. So he made no reply. Having nothing to do that afternoon, after the small quantity of good sap had been prepared, he spent the time with his lasso. It was remarkable how quickly one could become fairly proficient through constant, earnest practice. He could now swing the rope easily and hurl it accurately. If he continued to show improvement at the present rate he would be well able to hold his own when they returned to the ranch. “I believe in making hay while the sun shines,” he thought, “then after I’ve won my spurs in the bush it will be easier to get along at Las Palmas.” The next morning the contents of most of the cups were found to be in the same condition as on the previous day. After examining a number of the little, tough cakes David came to the conclusion that no matter what caused the trouble, he was not responsible for it. The cups were clean, for they were new ones. And the milk that trickled from the cuts was as it should be; it was only after it reached the little containers that it quickly coagulated. No! It was not his fault and not the fault of the trees; they had not soured overnight. Someone had visited his route and had tampered with his work. First he would try to find out what had been done and the next step would be to discover the guilty party. He took one of the small cakes and examined it carefully. The exterior was perfectly smooth. Then he cut it in half and looked at the texture of the interior of the mass. It did not differ from the outside. Not satisfied with this finding he divided one of the halves and when the knife had gone into it a little ways it scraped against some hard substance near the bottom. It was a large, black ant and he had cut it in two. That might be a clew as to what caused the difficulty. Acting on a sudden impulse he smelled of the pieces in his hand. There was a strong odor of acid, not unfamiliar to him. “Formic acid, of course,” he said half aloud. “Ants are full of it. It’s strong enough to curdle almost anything.”