nected the air valve. With a whistling rush, the air from the lock rushed into the sphere and he forced open the inner door. A stream of sea water drove against his feet through the open valve, and he reached for the valve to close it. The force of the water held it open for a moment, but he threw every ounce of his strength into the effort. The valve slowly closed.
It was beyond his strength to haul the heavy Doctor with his pressure diving suit through the restricted confines of the inner door, so Carnes wormed his way into the lock and with trembling fingers unscrewed the helmet of the Doctor's diving suit. The helmet clanged to the floor and Carnes scooped up his hands full of water and dashed it into the Doctor's face. There was no response and he was at his wit's end. He sprang for the radio to order the sphere hauled up when his glance fell on the oxygen tank. It took him only a moment to connect a rubber hose to the tank, and in a few seconds a blast of the life-giving gas was blowing into the scientist's face. Dr. Bird gave a convulsive gasp or two and opened his eyes.
"Shut off the juice, Carnes," he said faintly. "Too much of that's bad."
Carnes shut off the oxygen and Dr. Bird struggled to a sitting position and inhaled deep breaths.
"That was a narrow squeak, old dear," he said faintly. "Give me a hand and I'll climb in."
WITH the detective's aid he climbed into the sphere and Carnes fastened the inner door. Slowly the Doctor rid himself of the diving suit and lay prone on the floor, his breath still coming in gasps.
"Thanks for your warning about the time, Carnes," he said. "I knew that my air supply was running short but I was caught down there and couldn't readily free myself. I thought for a while that my time had come, but it wasn't so written. By the looks of things, I freed myself just in time."
"Did you find out anything?" asked the detective eagerly.
"I did," replied Dr. Bird grimly. "For one thing, the gold is no longer in the hold of the Arethusa."
"It's gone?"
"Clean as a whistle, every bar of it. A hole has been cut in the vault around the combination, and the bars slid back and the door opened. The gold has been stolen."
"Might it not have been stolen before the vessel sank?"
"The idea occurred to me of course, and I examined things pretty carefully. I know that the theft occurred after the vessel sank."
"How could you tell?"
"For one thing, the hole was cut with an under-water cutting torch. For the second, look here."
THE Doctor rolled up his trousers and showed the detective his leg. Carnes cried out as he saw huge purple welts on it.
"What caused that?" he cried.
"As I entered the vault, I stepped full into a steel bear trap which was set there for the purpose of catching and holding anyone who entered. Someone has visited the Arethusa, since she sank, and looted her, and also arranged so that any diver who got as far as the vault would never return to the surface to tell of it. Luckily for myself, I carried a heavy wrench and was able to free myself. Most divers don't carry such a thing."
"But who could have done it?"
"That's what we have got to find out, and we aren't going to do it down here. Give the word to have us hauled up; and, Carnes, don't mention anything about the looting of the vessel. Allow it to be understood that I couldn't get into the hold. We'll head back for New York at once. I want to have a few small changes made in this sphere before we use it again. While I am doing that, I want you to get hold of the Coast Guard or the Immigration Service or whoever it is that has the
