Watson, you can see everything. You fail, however, to reason from what you see. - Arthur Conan Doyle

There is nothing new under the sun. It has been done before.

As he spoke, he whipped a tape measure and a large round magnifying glass from his pocket. With these two implements he trotted noiselessly about the room, sometimes stopping, occasionally kneeling, and once lying flat upon his face... As I watched him I was irresistibly reminded of a pure-blooded well-trained foxhound as it dashes backwards and forwards through the covert, whining in its eagerness, until it comes across the lost scent. For twenty minutes or more he continued his researches, measuring with the most exact care the distance between marks which were entirely invisible to me, and occasionally applying his tape to the walls in an equally incomprehensible manner.

"I must apologize for calling so late," said he, "and I must further beg you to be so unconventional as to allow me to leave your house presently by scrambling over your back garden wall."