They went into the boat-house and sat at the open window looking over the sparkling broad. Frank said:
"I tell you what we must do. We must get Meredith to give us part of our holiday at the end of May or beginning of June, and we will take a cruise over all the rivers and broads of Norfolk and Suffolk. We could do it nicely in three weeks and scour every inch of the country in that time. What do you say? I will undertake to get my father's consent and Mrs. Brett's. What will Sir Richard say, Dick?"
"If you go, Frank, I am sure he will let me go; he has every confidence in you, and that you will keep us all out of mischief."
"I will try. Then it is agreed that we go."
"Most certainly. Frank will go in for birds'-nesting, Dick will catch butterflies and moths, and I must try to do something in the way of botany."
"And now it is time to go in; but before we go I just want to say that there is an old willow-tree down by the Broad which father thinks is an eyesore. I think that it is a likely tree in which to find the caterpillars of the goat-moth, which you know live on the wood of a willow, and eat long tunnels and galleries in it. What do you say to blowing the tree up with gunpowder?—it is only good for firewood, and perhaps we may find some caterpillars. Shall we get up early in the morning, bore a big hole into the heart of the tree, and fill it with gunpowder, set a train to it, and blow the whole affair up?"
Such a proposal was sure to meet with consent, and at seven o'clock the next morning the boys were down at the tree, boring a large hole into it.
The caterpillar of the great goat-moth feeds upon the wood of timber trees, notably oak, willow, and poplar. He is a smooth, ugly fellow of a red and yellow colour, with black feet and claws. He makes extensive galleries through the heart of a tree, eating and swallowing all that he gnaws away from the wood in his onward passage.
During the summer he eats his way slowly through the tree, making numerous and winding galleries; but during the autumn and winter he takes a siesta, first casing himself in a strong covering made of chips of wood and the silk which he weaves. The next summer he renews his work, and so he lives and grows for the space of three years, and then turns into the pupæ state, and emerges about July a dark brown but not unlovely moth, which lives for a few weeks and then lays its eggs and dies.
The boring was completed and was rammed full of coarse powder, and the mouth of the hole plugged up with a piece of wood. Through this plug a small hole was bored, and through this a long hollow straw made into a fuse was inserted.