Theory:

     At the end of the day the Man called the Horse and the Dog and the Ox together, and said, “Three, O Three, I’m very sorry for you; but that Humph-thing in the Desert can’t work, or he would have been here by now, so I am going to leave him alone, and you must work double-time to make up for it.”

 

     That made the Three very angry, and they held a panchayat on the edge of the Desert; and the Camel came chewing cud and laughed at them. Then he said “Humph!” and went away again.

 

     Presently there came along the Djinn who was in charge of All Deserts, rolling in a cloud of dust.

Explanation:
  
The "Man" or the master called all the three animals - horse, dog and ox together. He told them that he felt very sorry for them as the "Humph-thing" in the desert cannot do any work; if he could, he would have appeared for duty. The man refers to the camel as "Humph-thing" because all it does the whole day is humph-ing. It does not do any other work, so maybe he is not sure whether the animal is a camel or not! He further told the three animals that since the camel cannot do any work, he was about to divide the work amongst them, and therefore they must work twice their work time to cover up the duties of the camel.
 
The three animals got very angry, and they decided to hold a village council meeting where they discussed the problem and a solution has arrived. The meet was held on the edge of the desert. The camel came there chewing cud. (Cud refers to partly digested food that animals bring back from the stomach and chew further). He said "humph" again and went away.
 
Then there came along the Djinn who was in charge of all the happenings in the deserts. Since he is a supernatural character, he comes rolling in a smoky cloud filled with dust. Djinn is pronounced as jin, genie, genii etc. It refers to a supernatural character; it is a spirit that has unique powers and can take any form (humans or animals).

genie-2590056_1920.jpg
 
Meanings of difficult words:
  
Words
Meanings
panchayata village council, to discuss problems and arrive at a fair solution
cudpartly digested food that animals bring back from the stomach and chew further
Reference:
National Council of Educational Research and Training (2008). How the camel got his hump - Rudyard Kipling (abridged) (pp. 01-06). Published at the Publication Division by the Secretary, National Council of Educational Research and Training, Sri Aurobindo Marg, New Delhi.