Both Pierre and Marie clapped their hands. They knew well what was to happen next for they had often seen their father arrange the little arches of brush on which the silkworms were to climb and spin their cocoons. The placing of these rustic half-hoops was a delicate matter, since it was necessary to arrange them so that plenty of air might circulate through the space they enclosed; otherwise the worms would refuse to spin. Twigs or slender pieces of brush were set along the shelves in such a way that when bent the shelf above held them in place and made of them a series of miniature bridges, or arches. For certain varieties of caterpillars Pierre gathered branches of oak shoots with dried leaves clinging to them because Josef explained that this type of silkworm preferred that sort of twig on which to fashion its cocoon; other brush was stripped of leaves. And throughout the following days the greatest care had to be taken that nothing should interrupt the spinning. The things most to be dreaded were sudden noises; thunder-storms; and above all a drop in temperature, since chilly surroundings congealed the fluid silk in the ducts at each side of the silkworm, rendering it too thick for the creature to spin into fibre. The noise and the temperature could to an extent be controlled. But the thunder-storms! Those were another matter. Anxiously the Bretton family studied every passing cloud. "If a severe storm should wreck our crop now--at the very end--it would be cruel!" declared Pierre. "No matter how careful we are we cannot prevent some great black thunder-head from rolling over the mountains and down through the valley." "It is useless to worry, dear," answered his mother. "If such a storm comes it will be through no fault of ours." "It would raise havoc in our harvest just the same," cut in Josef. "The vibrations of thunder sound worse among the metal shelves. They catch the jar, and seem to hold and echo it. Your father told me about a man near Tours who had lightning wires along his shelves to protect his silkworms from electric currents. The wires carried off the worst of the vibration." "I wish we could afford to equip our silk-house that way," said Marie. "Just wait until we get rich. Maybe some day we can," answered Pierre gaily. Fortunately for the Brettons' silkworms, however, no electrical storm came.