What is the difference between “at the edge of the pit” and “on the edge of the pit”? 1) What is the difference between “at the edge of the pit” and “on the edge of the pit” in the context below? 2) What is the meaning of "sand pits"? "There, among some young pine trees and furze bushes, I stopped, panting, and waited further developments. The common round the SAND PITS was dotted with people, standing like myself in a half-fascinated terror, staring at these creatures, or rather at the heaped gravel AT THE EDGE OF THE PIT in which they lay. And then, with a renewed horror, I saw a round, black object bobbing up and down ON THE EDGE OF THE PIT. It was the head of the shopman who had fallen in, but showing as a little black object against the hot western sun. Now he got his shoulder and knee up, and again he seemed to slip back until only his head was visible. Suddenly he vanished, and I could have fancied a faint shriek had reached me. I had a momentary impulse to go back and help him that my fears overruled ." (The War of the Worlds by H. G. Wells) Thank you!