shrubs growing in the cracks of the rock. And the canal here left off running along the top of the hill and started to run on a bridge of its own—a great bridge with tall arches that went right across the valley.
Bobbie drew a long breath.
"It is grand, isn't it?" she said. "It's like pictures in the History of Rome."
"Right!" said the Doctor, "that's just exactly what it is like. The Romans were dead nuts on aqueducts. It's a splendid piece of engineering."
"I thought engineering was making engines."
"Ah, there are different sorts of engineering—making roads and bridges and tunnels is one kind. And making fortifications is another. Well, we must be turning back. And, remember, you aren't to worry about doctor's bills or you'll be ill yourself, and then I'll send you in a bill as long as the aqueduct."
When Bobbie had parted from the Doctor at the top of the field that ran down from the road to Three Chimneys, she could not feel that she had done wrong. She knew that Mother would perhaps think differently. But Bobbie felt that for once she was the one who was right, and she scrambled down the rocky slope with a really happy feeling.
