The suck of the water as it took the beginning of the last steep pitch was frightful, and Thornton knew that the shore was impossible. He scraped furiously over a rock, bruised across a second, and struck a third with crushing force. He clutched its slippery top with both hands, releasing Buck, and above the roar of the churning water shouted: "Go, Buck! Go!"
It's from 'The Call of the Wild' by Jack London.
In the above sentence, 'a second' could be understood 'in the second place' while 'a third' be 'in the third place'? And then where is 'a first'?
May be it is a stupid question, but I don't understand the above sentence clearly.