Magwich first describes Compeyson says “I’d crack wi’ this poker, like the claw of a lobster”
In this simile Dickens creates the connotation that it was easy and he done it without thinking. A lobster could crack a skull easily and its like second nature to it.
We know this to be easy for Magwitch as he hates compeyson and scarafced hia freedom to put him back in jail

 

“My sister, Mrs. Joe Gargery, was more than twenty years older than I, and had established a great reputation with herself and the neighbors because she had brought me up “by hand.” Having at that time to find out for myself what the expression meant, and knowing her to have a hard and heavy hand, and to be much in the habit of laying it upon her husband as well as upon me, I supposed that Joe Gargery and I were both brought up by hand.”

 

 

My task was to find some irony in the book and i’ve found irony here. Being brought up by hand’s connotation means in a personal and caring way. But the denotation which you wouldnt usually use is literal . In this context it means being hit . The way how the two are completely different is ironic