"I have been busy, girls," replied David. "Never busier in my life. But I believe I've struck it at last. It will not be long, now, before I turn into a bird."
"Oh, do show it to us!" cried Grace. "Where is the model?"
"In my workroom," he replied. "If you are very good, and will promise to say nothing to the others, I'll give you a peep this afternoon. When I signal to you from the music room, by sounding three bass notes on the piano, start upstairs and I'll meet you on the landing. You may ask why this mystery? But I know girls, and if all those chattering freshmen are allowed to come into my room they are sure to knock over some of the models, or break something, and I couldn't stand it."
The three girls entered the large and imposing drawing room where Miriam, in a beautiful pink mulle, trimmed with filmy lace insertions, received them with unusual cordiality; and presently they all repaired to the dining room where ice cream and strawberries were served with little cakes with pink icing. It was, as a matter of fact, a pink tea, and Miriam's cheeks were as pink as her decorations. She looked particularly excited and happy. Each of the three chums had just swallowed her last and largest strawberry, saved as a final relish, when three low notes sounded softly on the piano in the adjoining room.
In the hum of conversation nobody had noticed David's signal except Grace and her friends, who strolled into the music room where he was waiting.
"Come along," he said, leading the way up the back stairs, "and please consider this as a special mark of attention from the great inventor who has never yet made anything go. Where's Anne?"
"I suppose she is resting," answered Grace. "She had just about reached the end of her strength to-day."
"But she'll win the prize, I hope," continued David.
"We are all sure of it," answered Grace, in emphatic tones.
David opened the door into his own private quarters, which consisted of a large workroom with a laboratory attached, where he had once worked on chemical experiments until he had become interested in flying machines.