Wait a moment. Retain this clearly in your mind, and I will proceed to the second point.
It has been remarked by the less stupid of psychologists—and that is not saying much—that cunning and intelligence are not often combined. Conversely, as Dr. Nancy Neerly shrewdly remarked, when her assistant at the Hospital for Nervous Diseases, gonophed her microscope, extreme incompetence is often accompanied by cunning. Nothing is more cunning than your half-wit.
Getting that principle firmly into your head, you will appreciate that when Professor de Bohun slunk out in the evening after his cousin's departure for town, into the neighbouring suburban villas of Bakeham (which, for one thing, fringed the Park—the de Bohuns had long ago screened it by a dense row of quickly-growing timber—and for another, provided the Home Secretary with a considerable part of his insufficient income) his action was not unconnected with that upon which his mind had been exercised for now nearly twenty-four hours.
He sought a policeman, and said with a sudden squeak which made that high official jump:
"Oh! Can you tell me if anyone round here sells scientific instruments? Optical instruments? Electrical instruments? ... Instruments?"
"Wot?" said the policeman.
"Let us say ... ah, for instance," went on the squeaky voice, "clinometers.... Shall we say Clinometers? Clinometers? ... Yes! Clinometers!"
"Pass along!" said the policeman. "Pass along!" And there was that in his eye of a man who hesitates between a verdict of lunacy and arrest for leg-pull.
"But, Constable ..." pleaded the unfortunate cadet of an ancient house.
"Pass on! Pass on!" boomed the tyrant, and as there was a difference of at least three octaves between the two men's voices, the unfortunate Professor obeyed the double bass, crossed the street at the risk of his life, and wandered inanely past the shop windows.