The Saint reached for a piece of paper.
"Do you know anything about chemistry?"
"Nothing at all," confessed Mr. Parnock. "But I have a friend who understands these things."
Simon wrote on the paper and passed it over. Mr. Parnock studied it wisely, as he would have studied a Greek text.
Cu + Hg + HNO 3 + St = CuHgNO 3 + H 2 O +NO 2
"Aha!" said Mr. Parnock intelligently. He folded the paper and stowed it away in his pocket-book, and stood up with his smooth fruity chuckle. "Well, Mr. Smith, you run along now and attend to your business, and come and have lunch with me on Thursday and let's see what we can do about your invention."
"I can't tell you how grateful I am to you, Mr. Parnock," said the Saint almost tearfully as he shook the patent agent's smooth fat hand; but for once he was speaking nothing but the truth.
He went down to see Inwood again later that afternoon. He had one thousand pounds with him, in crisp new Bank of England notes; and the shabby old chemist's gratitude was worth all the trouble. Inwood swallowed several times, and blinked at the money dazedly.
"I couldn't possibly take it," he said.
"Of course you could, uncle," said the Saint. "And you will. It's only a fair price for your invention. Just do one thing for me in return."