“I know of it,” the man admitted. “Drukker uses it in his book on world lines. My mathematics, however, are not of the physicist’s type. Had I not become enamored of chess”—he smiled sadly—“I would have been an astronomer. Next to manœuvring the factors in a complicated chess combination, the greatest mental satisfaction one can get, I think, is plotting the heavens and discovering new planets. I even keep a five-inch equatorial telescope in a pent-house on my roof for amateur observations.”
Vance listened to Pardee with close attention; and for several minutes discussed with him Professor Pickering’s recent determination of the trans-Neptunean O,[21] much to Markham’s bewilderment and to the Sergeant’s annoyance. At length he brought the conversation back to the tensor formula.
“You were, I understand, at the Dillards’ last Thursday when Mr. Arnesson was discussing this tensor with Drukker and Sprigg.”
“Yes, I recall that the subject came up then.”
“How well did you know Sprigg?”
“Only casually. I had met him with Arnesson once or twice.”
“Sprigg, also, it seems, was in the habit of walking in Riverside Park before breakfast,” observed Vance negligently. “Ever run into him there, Mr. Pardee?”
The man’s eyelids quivered slightly, and he hesitated before answering.
“Never,” he said finally.
Vance appeared indifferent to the denial. He rose and, going to the front window, looked out.