The look on Marvin’s face was ghastly. At last he managed to ejaculate, “Only twenty-seven!” “Yes,” muttered Grein, “and any one of his frequencies was worth more to England than the whole damned British army!” Marvin’s unconscious fingers closed like clenching tools as he dully uttered one word: “Lead!” “Exactly. Lead driven through the one brain that really understood lead. Better drop your fuels and study lead.” “No. I’m not in that class.” “Who knows what class you’re in? I’m no Boltwood, and I’m too busy to pace you, but I’ll see that you have some salts and minerals to work with, and you can have a corner to yourself for the rest of the year.” Chapter 7. Nitrogen When Dr. Rich had broken his news to his wife, they both breathed easier. And Mrs. Rich could feel still more relief coming. She had said nothing about her occasional shortness of breath, but she looked forward eagerly to the pure cold air of the north. And now that the college year was over and the faculty scattered, there need be no sadness of a farewell dinner. There were persons in the faculty who were conscious of nitrogen, but the Riches were not. They were literary and easily deceived. They took their nitrogen as it came, and really thought it was peas and beans and eggs. They never stopped to think that they were constantly inhaling and exhaling nitrogen without brushing a single electron off its surface. Only Horatio was an exception. He knew the stuff. He was going to raise it as cow-peas and plow it under. He had no farm as yet, but a tenancy had been promised him on the Canadian side of the St. Mary’s, and when his folks were all packed up to leave Warrenville forever, he went ahead by train to open the cabin for them. The rest of the family followed by steamer. The evening was pleasant as they watched the Chicago river widen before them into Lake Michigan. Their first objective was Mackinac island, famous long before the days of railroads, the point at which three great lakes meet. They lie like a clover leaf, and the cabin of Dr. Rich stood by the channel that connects the uppermost leaflet with the other two. To change the figure to that which appears in a certain fountain, Lake Superior is a brimming shell from which a spillway leads the water down. The beauty spreads westward into Michigan, and eastward into Huron. Thence it narrows into Erie, drops with a roar and a rainbow into Ontario, and rushes to the sea. The Riches dwelt by the first spillway, which forms part of the boundary between the United States and Canada. It is called the St. Mary’s river, and is perhaps the only waterway along which bear and moose peer from their covert at great steamers going by. No other stream carries so great a tonnage through so wild a country. Iron comes down, and coal goes up, and there are points where a lump of either can be tossed ashore as the great steam barge slips past.