Why could the narrator see nothing but the sky?

I lay down on the grass, which was very short and soft, where I slept sounder than ever I remembered to have done in my life, and, as I reckoned, about nine hours; for when I awaked, it was just day-light. I attempted to rise, but was not able to stir: for, as I happened to lie on my back, I found my arms and legs were strongly fastened on each side to the ground; and my hair, which was long and thick, tied down in the same manner. I could only look upwards; the sun began to grow hot, and the light offended my eyes. I heard a confused noise about me; but in the posture I lay, could see nothing except the sky. In a little time I felt something alive moving on my left leg, which advancing gently forward over my breast, came almost up to my chin; when, bending my eyes downwards as much as I could, I perceived it to be a human creature not six inches high, with a bow and arrow in his hands, and a quiver at his back. I was in the utmost astonishment, and roared so loud, that they all ran back in a fright; and some of them, as I was afterwards told, were hurt with the falls they got by leaping from my sides upon the ground. However, they soon returned, and one of them, who ventured so far as to get a full sight of my face, lifting up his hands and eyes by way of admiration, cried out in a shrill but distinct voice, Hekinah degul: the others repeated the same words several times, but then I knew not what they meant.