Marvin finally accepted Grein’s invitation and abandoned the study of fuels. He was getting nervous about the achievements of German chemists. Those laborious beasts, themselves sixty percent oxygen, were uniting atmospheric oxygen and nitrogen with alarming results. They had placed the German farmer beyond fear of famine and the German army beyond fear of ammunition shortage. All they needed now to conquer the world was to capture the heat hidden in atomic nuclei. Suppose they should stumble on the secret while studying lead!

Grein was able to supply him with a variety of radioactive minerals, and he plunged into the analysis of them to find out how lead derived from radioactives differs from ordinary lead.

In September he was interrupted by a letter from Jimmy, who wrote that he was spending several months in getting acquainted with the Ferry plant. It was halfway out to a place called Warrenville, which Marvin perhaps knew.

Marvin read the letter with pride. He did not know Warrenville, but he knew Jimmy, and was delighted that Asher Ferry was sizing him up correctly. But Jimmy had not seen Gratia. She and her mother had been out of town all summer, and she had now returned to Eglantine.

Thus reminded, Marvin bought his car and drove out to Wickford. He first went to Mrs. Hogg, and told her that he was going over to Eglantine to take Miss Coggeshall and Miss Ferry driving. He said that there was plenty of room and that he should feel honored if she would make one of the party. Mrs. Hogg courteously thanked him and remained on her porch.

But at Eglantine his welcome was different. Gratia was greatly pleased that he had bought a car, and knew that he had done so for the purpose of enjoying her company. Thereafter, every Saturday afternoon at four o’clock precisely, she knew that he was turning in through the sweetbrier, smiling and handsome and ready for nonsense unless she mentioned Germans.

Miss Kate always went with them and always sat alone. Gratia did most of the talking. Being good in arithmetic but not so good in college algebra, she saved up puzzles for him. She would read off her problem and wait. Marvin would smile ahead at the autumnal road, perhaps dodge a stray hen, and speak the answer. After that she was ready to discuss the country, and would turn round to ask about the estates. Finally she would tell about her week, and ask him about his own.

She never learned much about his week. He was too busy admiring her hair, which was about the tint of pale nasturtium, with as faint and pure a fragrance. He took delight in the sound of her voice, her dark blue eyes, her grace. She was a constant lesson in refinement, and when he danced with her he knew that this was the right limit of pleasure that he might take in any girl’s sweetness before he was married.

The girls of Eglantine presumed to regard this lively friendship as an engagement. They delighted to swarm about Marvin in the hope of embarrassing him, but they never succeeded. His impartial “darlin’” was ready for them all, and beyond that he presumed no further.

Cynthia was back for the holidays, and once more sang to him. This time it was the Liebestod from “Tristan and Isolde,” and she put all her soul and all her brand-new New York training into it. She did it so well that she seemed to die before his eyes, note by note her breath resigning. He told her he should never forget those marvelous progressions.

After that, in the early months of 1916, Cynthia was no more thought of, and even the delightful companionship with Gratia ceased for a while. He had sought girls as instinctively as a metal seeks the most abundant of the elements, and found them all slightly intoxicating, but none had crumbled him into white sparks.

His love was lead. He was less enchanted by carbon than by her sister, who had sung Moseley to sleep to prevent him from revealing her music to the world. But Marvin, listening in, began to recover that music, thrill on thrill. It seemed to him to advance in close chords like those in which Cynthia had so happily died to him.

To put it less figuratively, he began to suspect that no fewer than ten substances may pass as lead. They are what Soddy had called isotopes, or equals in place. The Moseley number for lead is 82, and Soddy had made it clear that at least one radioactive substance deserves that number, and that at least one inactive lead is lighter than ordinary lead. Marvin now conceived at least three inactive and three active leads, weighing 206, 207, 208, 210, 212, 214. This was maddeningly close to transmuting inactive into active, but he saw no hope of turning the trick. He had to content himself with proving that there really is an inactive lead as light as 206, and after much search and labor he discovered it in a certain Norwegian mineral.

This was getting on, but not fast enough to stop any Germans. They were steadily advancing, preceded by hot lead of weight 207. Well, there was plenty of that sort in Missouri, and he concluded that America ought to do more than sell it to the Allies. She ought to project a little of it, hardened with antimony, herself.