how did mortimer inadvertently insult holmees

Mortimer inadvertently states that Holmes is the "second highest" expert in Europe.

Recognizing, as I do, that you are the second highest expert in Europe—"

"Indeed, sir! May I inquire who has the honour to be the first?" asked Holmes with some asperity.

"To the man of precisely scientific mind the work of Monsieur Bertillon must always appeal strongly."

"Then had you not better consult him?"

"I sa id, sir, to the precisely scientific mind. But as a practical man of affairs it is acknowledged that you stand alone. I trust, sir, that I have not inadvertently—"

"Just a little," said Holmes. "I think, Dr. Mortimer, you would do wisely if without more ado you would kindly tell me plainly what the exact nature of the problem is in which you demand my assistance."