And if you think it is a simple matter to make a nest of clay, just go to the wisest architect you know and ask him these questions. How many hodfuls of clay, each holding as much as half a thimble, would it take to build the wall of a room just the right shape for a swallow to sit in while she brooded her eggs? How large would it have to be inside, to hold four or five young swallows grown big enough for their first flight? How thick would the walls have to be to make it strong enough? What sort of curve would be best for its support against a perfectly straight wall? How much space would have to be allowed for lining the room, to make it warm and comfortable? How can the clay be handled so that the drying sun and wind will not crack the walls? What is the test for telling whether the clay is sticky enough to hold together? How much of the nest must be stuck to the cliff so that the weight of it will not make it fall? If the architect can answer all those questions, ask him one more: ask him if he could make such a nest with the same materials the birds used, and with no more tools? Well, Eve and Petro could and did. It was big enough and strong enough and shaped just right; and when it was nearly done and nearly ready for the soft warm lining, That Boy climbed the ladder and knocked it down with his hand. There it lay, Eve and Petro's wonderfully modeled nest of clay, broken to bits on the ground and spoiled, oh, quite spoiled. There is a saying that it brings bad luck to do harm to a swallow. What bad luck, then, had the hand of That Boy brought to the world that day? [Illustration: _They always chatted a bit and then went on with their work, placing their plaster carefully._] Bad luck it brought to Eve and Petro, who had toiled patiently and unafraid beside the ladder-top, with faith in those who climbed quietly to watch the little feathered masons at their work. But now the walls of their home were broken and crumbled, and their faith was broken and crumbled, too. In dismay they cried out when they saw what was happening, and in dismay their swallow comrades cried out with them. Fear and disappointment entered their quick hearts, which had been beating in confidence and hope. People who climbed ladders were not beings to trust, after all, but frightful and destroying creatures. This had the hand of That Boy brought to Eve and Petro, who looked at the empty place where their nest had been, and went away.