Analysis of John Mouldy

I spied John Mouldy in his celler,
Deep down twenty steps of stone;
In the dusk he sat a-smiling
Smiling there all alone.

He read no book, he snuffed no candle;
The rats ran in, the rats ran out,
And far and near, the drip of water
Went whisp'ring about.

The dusk was still, with dew a-falling,
I saw the Dog-star bleak and grim,
I saw a slim brown rat of Norway
Creep over him.

I spied John Mouldy in his celler,
Deep down twenty steps of stone;
In the dusk he sat a-smiling
Smiling there all alone.