"Hush!" I whispered; "Bob has just got the range of a supply train on the far side of the rockery, and if Nevin (Nevin is the Crown Prince of Wurtemberg) doesn't get the longitude of Bob's battery in the next minute or so it's all up with his day's rations." Suddenly Bob rose and made some calculations on an old envelope. "That means three rounds battery fire," I said, "and the Prince loses his lunch." Not satisfied with this success, Bob went indoors and looted the hall of three walking-sticks and Margery's new sunshade. "What's he going to do now?" said Margery, with one eye on the sunshade. He walked to the far end of the lawn and manoeuvred in a small circle. "The water-jackets are boiling," I replied, "and they've run out of cold water. He's divining with the sunshade. Look!" Bob suddenly drove the sunshade into the ground. There was a sharp crack and--well, he found another iron. Of course he tried to explain to Margery that it was an absolute accident and he only wanted to get a sighting post; but that was mere self-effacement, and I said so. Things began to happen quickly after this, and if Private James Thompson had not put in an unexpected appearance they might have completed the job without any further difference of opinion. In the merry days before war was thrust upon us, James Thompson was an architect of distinction. Obviously an architect of distinction can reduce the difficulty of laying out a tennis-court to an elementary and puerile absurdity. For half-an-hour the demonstration was carried on in the garden, and, after Private Thompson had twice been threatened with arrest for using insubordinate language to a superior, it was decided to finish the discussion in my study, assisted by the softening influence of the Tantalus. Not for a hundred pounds would I have ventured into the study. I picked up _The Gardening Gazette_ and engrossed myself in an interesting piece of scandal about the slug family. Suddenly Margery appeared at the double. "Do you know," I exclaimed excitedly, "it was the wireworm after all." "Come on," Margery panted irrelevantly, "buck up and we can finish it before they come out again." In her hand she held a tape-measure and an official diagram of a tennis-court. Five minutes later the experts emerged from the house. "Hullo!" exclaimed Nevin aggressively, "what have you been up to?" "Oh," I replied, flicking over a page on weed-killers, "Margery and I thought we had better find the remainder of the tennis-court while you were having a rest. Margery's gone for a ball of string, and if Bob fetches the marker you can mark the court out now." Nevin's retort was addressed solely to Private James Thompson, who had in an unfortunate moment given way to laughter of an unmilitary character. * * * * * [Illustration: THE AMATEUR DETECTIVE. {Cartoon, four panels, each with two gentlemen gazing skyward, bombs exploding nearby. One is using binoculars.}