What is all that but an exaggeration of the police’s standard principles of searching which are based on only one set of ideas about human ingenuity to which the Captain, in his long routine career, has become accustomed.
Do you not see that he has taken it for granted that all men proceed to conceal a letter in a way similar it there? And do you not also see that such methods of concealment are only used for ordinary occasions by people of ordinary intellect? All cases of concealment in this manner are presumable and thus the discovery of the hidden object depends not on the care, patience and determination of the searcher.
When the case is very important, or the reward is great, these qualities have never been known to fail.