Absolute Pressure Read Online Free

dry-land lessons on scuba diving.
    There is also a back room with a work bench. It’s where we fill the scuba diving tanks with air and do repairs.
    The fourth room is Uncle Gord’s office. It is tiny. Hardly larger than his messy desk. He always keeps the door locked so that customers don’t wander in.
    He was standing at the work bench. Tools were scattered across the top of it.
    The valve parts of my scuba tank were in front of him.
    I moved beside him to look at the tank.
    â€œSee,” he said, pointing. “Look at where the spring broke apart.”
    The spring was from the valve. It was strong enough to keep the valve partly closed against the air pressure inside the tank. Except it had broken into two pieces.
    â€œYes?” I wasn’t sure what he meant.
    â€œUse the magnifying glass.”
    I did. As I looked at it up close, he kept talking.
    â€œIt’s like a tree you cut with a saw,” he said. Uncle Gord loved using examples. “The cut is smooth most of the way through. But when the tree falls, the last little bit breaks away and leaves a jagged edge.”
    He was right. On one side of the broken spring, it was shiny, as if it had been snipped halfway through. The other side was jagged, like it had been ripped apart.
    â€œI don’t get it,” I said.
    â€œI do,” he told me. He frowned. “And I don’t like it.”
    I waited.
    â€œYou know all about water pressure,” he said.
    I nodded yes. It had just about killed me the day earlier.
    â€œSomeone took this valve apart and cut most of the way through the spring. Then he put it back together. The spring was still strong enough to hold in shallow water. But in deeper water, it would only be a matter of time until the pressure blew it apart.”
    â€œIn other words,” I said, “someone wanted this accident to happen in deep water.”
    â€œExactly. What if you had been deep inside the shipwreck when this happened instead of near the opening?”
    I gulped. Sometimes it takes ten minutes just to swim out of a wreck.
    â€œI’d be dead,” I told him.
    Uncle Gord stared at me for nearly a minute. He has light blue eyes. They didn’t blink as he thought about it.
    â€œI already know a lot of the story,” he finally said. “You dove instead of Judd.”
    â€œYes, sir,” I said.
    â€œEven though I had told you I wanted you on the surface in the boat.”
    â€œI’ve dived lots,” I said. “I’m certified. You taught me to be careful. I didn’t think you’d mind.”
    â€œWhat I mind is him not doing what I paid him for. He was supposed to go down into the wreck. Not you.”
    â€œYes, sir.”
    Uncle Gord stared at me for another minute. I remembered some stories I’d heard about him getting into fights when he was younger. I’d heard he was tougher than most guys twice his size. By the cold look in his eyes, I was able to believe it.
    â€œTell me,” he said. “Did you ask Judd if you could make the dive? Or did he ask you?”
    My body suddenly felt as cold as Uncle Gord’s eyes. I understood his question. If Judd had asked me to go down, maybehe knew about the valve and that it would bust in deep water.
    â€œI asked to dive,” I said. “Honest. It was my idea. I was bored and wanted something to do. It was my fault this happened.”
    Uncle Gord slammed the work bench so hard that a wrench jumped and fell to the floor.
    â€œIt wasn’t your fault,” he said, his face angry. “It was the fault of whoever wrecked the valve spring.”
    He hit the table again. “I’m going to find out who did this.”
    Uncle Gord took a deep breath. He waited until he was calm.
    â€œIan,” he said, “you and I are going to keep this a secret. That way, the person who did it won’t know we’re looking for him.”
    â€œWhat about the police?” I