Perhaps he found the human machine as worthy of interest as the works of watches and clocks.

Anyhow, in his leisure moments, which were few, he would discuss curiously with Mary the hidden springs that kept the human machine in motion, the strange workings and convolutions of it.

From the very early age when she began to be a comfort and a companion to her father, Mary had been accustomed to such speculations as would have written Walter Gray down a madman if he had shared them with the grown people about him rather than with a child.
Mary was the child of his romance, of his first marriage, which had lasted barely a year.
He never talked of her mother, even to Mary, though she had vague memories of a time when he had not been so reticent.

That was before the stepmother came, the stepmother whom, honestly, Walter Gray had married because his child was neglected.

He had not anticipated, perhaps, the long string of children which was to result from the marriage, whose presence in the world was to make Mary's lot a more strenuous one than would have been the case if she had been a child alone.
Not that Mary grumbled about the stepbrothers and sisters.