Tom Slade at Bear Mountain by Percy Keese Fitzhugh

The circle of brightness had disappeared. Brent's foot and the rock and the snake's head were blotted out. He could see nothing now, only feel the coiled reptile around his leg. Instinctively, he pressed more firmly. The snake relaxed a trifle, being probably less agitated in the darkness.

Even in his frightful predicament, Brent noted with interest how every instinctive impulse of the snake was evidenced in the pressure and relaxation of its coiling body. But he was all but panic-stricken now in the enshrouding darkness; he could only feel and hear his would-be assailant. The sudden failure of that little flashlight was like the sun going out of his life.