She was above all a most formidable female. She had once been a famous athlete, and even now the muscles were still clearly in evidence. You could see them in the bull-neck, in the big shoulders, in the thick arms, in the sinewy wrists, and in the powerful legs. Looking at her, you got the feeling that this was someone who could bend iron bars and tear telephone directories in half. Her face, I'm afraid, was neither a thing of beauty nor joy for ever. She had an obstinate chin, a cruel mouth, and small arrogant eyes.
From Matilda by Roald Dahl
What is the purpose of this passage?