Question

How can the reader tell that the passage is written from the point of view of the 19th century British child

Answer 1

If the writer uses shorter words and simpler adjectives to describe things, as though a child may be speaking then you will be able to tell. Look for words a child might have said in that time period, such as calling their mother "Mum", or watch their actions, like if they have to grab a step-stool to reach the cupboards.