What is some verbal irony in Conan Doyle's "The Adventure of the Speckled Band"?

There is plenty of verbal irony in the encounter between Sherlock Holmes and Dr. Grimesby Roylott right after Roylott's stepdaughter Helen Stoner has departed for home. Roylott tries to intimidate Holmes into telling him why Helen came to Baker Street and what she told him. Holmes is characteristically fearless and frigidly polite. His replies to Roylott are ironic because he is saying the opposite of what he is thinking. For example:

“I am Dr. Grimesby Roylott, of Stoke Moran.”

“Indeed, Doctor,” said Holmes blandly. “Pray take a seat.”

“I will do nothing of the kind. My stepdaughter has been here. I have traced her. What has she been saying to you?”

“It is a little cold for the time of the year,” said Holmes.

“What has she been saying to you?” screamed the old man furiously.

“But I have heard that the crocuses promise well,” continued my companion imperturbably.

The author, Sir Arthur Conan Doyle, probably had a special purpose for having some of Holmes' ironic replies deal with the cold weather. The reader is going to wonder why the poisonous snake would stay on the bed and not try to escape when it found itself free of Dr. Roylott's control. The answer is that the snake comes from a tropical climate. It would be more likely to seek warmth than to try to escape from the room, especially when the weather is so cold. Julia Stoner was killed almost exactly two years earlier, when the weather would have been equally cold.

Holmes' dialogue is frequently ironic. That is one of his characteristics. He is being ironic at the very end of the tale when he tells his friend Watson:

"In this way I am no doubt indirectly responsible for Dr. Grimesby Roylott's death, and I cannot say that it is likely to weigh very heavily upon my conscience.”

He is really glad that Dr. Roylott was killed by his own snake after the detective angered it and drove it back up the bell-rope and through the ventilator. That eliminates him as a threat to Helen and rids the world of a dangerous madman. Roylott's death will not weigh on Holmes' conscience at all.