Theory:

     “That was close! What shall we do now?” asked my master.

     “Well, sir, we can’t drive over this big tree and we can’t get round it. We must go back to four cross ways. Then it will be about six miles before we get to the wooden bridge again. It will make us late, but black beauty is fresh.”

     This happened sometimes when the river was flooding, so Master did not stop. We were going along at a good speed, but the moment my feet touched the ground the first part of the bridge, I felt sure that something was wrong. I dared not go forward. I made a dead stop.
 
     “Go on, Beauty", said my master, and gave me a touch of the whip. But I dared not move. He gave me a sharp snap of the whip. I jumped, I jumped, but I dared not go forward.

     “There is something wrong sir”, said John. He got down from the cart and came to my head. He took hold of my bridle and tried to lead me forward. “Come on, Beauty. What’s the matter?” Of course, I could not tell him what the problem was, but I knew very well that the bridge was not safe.
Explanation:
  
Master exclaimed that it was close! He meant the tree could have fallen on them anytime. He asked John about what to do next.
 
John told Master that they cannot drive further because of the fallen tree and that they cannot go around it also. He added they must go back to the four crossways, and then it will take about six miles before they reach the wooden bridge again. It will be late by then, but the horse black beauty still looked fresh. He meant the horse was steady and good to go.
 
The Master had seen such things happen during floods, so he did not stop. They were travelling along at a good speed when the horse suddenly felt something. The horse felt the ground with his feet, in the first part of the bridge and felt something was wrong. He did not dare to move forward a single step. He made asudden, sharp stop.
 
dead stop.png
The horse came to a dead stop!
  
The Master did not understand why Black Beauty stopped; he asked him to go on. He lightly touched him with his whip to make the horse move. But the horse did not dare to move. Then the Master gave a whack with the whip. The horse jumped in pain again and again but did not move forward.
 
John found that there was something wrong. He got down and came near the horse. He caught the bridle and guided him to move forward. The horse could not explain to him the problem that he felt. But he knew that the bridge was dangerous to cross. The horse had an instinct, a feeling that it was not safe, and it believed in it strongly. Even if he got whip lashes, he did not move - he believed in his instincts.
  
Meanings of difficult words:
  
No.
Words
Meanings
1
a dead stopa complete, sudden stop
2
whip
(noun) a strip of leather attached to a handle, used for urging on an animal
Reference:
State Council of Educational Research and Training (2019). Term-1 English Standard-8. When Instinct Works - Anna Sewell(pp. 145-151). Published by the Tamil Nadu Textbook and Educational Services Corporation.