“There is a formula for each,” he said. “In these cow-pictures, for instance, you will see that there is a definite proportion of two-thirds cow to one-third landscape. Venetian canal scenes like this must be exactly fifty per cent reflection. Last week I worked up a batch of South Sea pictures using the Gauguin formula. It is very simple.”

Mr. Wilkins was delighted with Rollo’s clam-shell.

“I must do some!” he said. “Could you leave it here?”

“Yes, indeed, gladly,” said Rollo.

“And what have you been working on to-day?” said Uncle George.

“Just a little summer work,” said Mr. Wilkins. “Here it is.”

He removed a cloth which covered an easel, and Rollo gazed with awe and admiration at a picture of a beautiful young lady who was about to go in bathing without any bathing suit. Rollo had never seen anything like it before and he was much interested.

“She is a hum-dinger,” said Uncle George. “Who is she?”

While Mr. Wilkins and Uncle George chatted in a corner Rollo examined the picture closely and was really very sorry when Uncle George told him it was time to go.