Question

why does the mirror appear to be a lake in the second stanza what aspect of the mirror do you think is being referred to here???

Answer 1

The mirror in the second stanza appears to be lake because it is the quality of reflection on any image of what appears before it like a lake. When anything falls on it, it sinks into it, just like the lake, the mirror also swallows whatever it sees. Here, the depth is being denoted.