In Mrs. Trenchard’s absence there was to be no midday dinner. After clearing up the mess with the assistance of one of the dairy-maids (who called it "a rare messopotamia as anybody ever did see"), the two lads went to join the farmer at lunch in the fields. "That there invention, now," said Mr. Trenchard. "Hev it worked?" "Splendid!" said Eves, emphatically. "We’ve got two good sacks of soot and scared a slug." "It don’t take a mighty deal to do that, sir," said the farmer with a smile. "I’ll find that soot useful, and I’m much obleeged to ’ee, to be sure." "Oh, but, Mr. Trenchard, could you spare me some?" said Templeton. "For another invention," Eves added. "He’s got a jolly good idea for protecting our ships from the U-boats, and soot’s in it." "As much as you do want, surely. I’d gie more’n a little to scrimp them there engines of iniquity." "And perhaps you could help me with something else," said Templeton. "I want a sort of metal box; any old thing would do, something that’s no good for anything else." "I can find ’ee summat, I b’lieve. There be an old tank in the shed behind the dairy, where I keep th’ old tricycle." "A tricycle!" exclaimed Eves. "What about that for number four, Bob?" "The very thing! Will you lend it or sell it, Mr. Trenchard?" "I’ll take no money from a young gent as is inventing for his country, danged if I will. ’Tis a old ancient thing that I bought five-and-twenty year ago for me and the missus." "A sociable!" cried Eves. "We are in luck’s way." "’Tis called such, I b’lieve," said the farmer. "Ay, ’tis many a year since the missus and me went gallivanting about the country. She were a nesh young maid then, so to speak it; you wouldn’t think it to see the size she’ve growed to. I’ve kep’ th’ old thing for the sake o’ them gay young days." "If you can spare us this afternoon, I’d like to experiment with it," said Templeton. "Surely, and welcome, and I hope ’twill serve ’ee." Hurrying back to the farmhouse they drew the tricycle from the shed and tried its paces over the yard. It was rusty and stiff, but a little oil eased the parts, and Templeton was delighted with his number four. The tank of which Mr. Trenchard had spoken was made of galvanised iron, and had several holes pierced in each side. "The very thing!" cried Templeton. "We’ll make some more holes at different heights, Tom." "What for?" "My idea is to rig up some trays inside the tank, one above another; there are several old sheets of iron lying about. They’ll hold the soot and combustibles." "By George! we forgot to ask Mother Trenchard to bring some firelighters." "Never mind about them for the moment. We’ll bore holes just above the trays, and put in some straw soaked in paraffin, and light it. Then when we start there’ll be a fine draught through the holes." "Splendid! But shan’t we be fairly choked?" "Of course we’ll rig up the tank behind us; the smoke will all blow back."