Sherlock Holmes Consulting Geologist
Even though the much-admired Sherlock Holmes is a fictional character, his working methods do provide a sound
foundation for geological researchers. It is almost always the case that the world's greatest consulting detective is
obliged to reconstruct past events, often involving a homicide victim who is understandibly not very communicative.
One of the most powerful tools Holmes wields comes from the guiding principle of deduction: "when you have eliminated
the impossible, whatever remains, however improbable, must be the truth." From The Sign of the Four (1890)
[] also featured in, among others,
The Adventure of the Beryl Coronet []
and The Adventure of the Bruce-Partington Plans []
A comparatively rare jewel is utilized in Silver Blaze. The title character is a race horse which goes missing before a race at the same time as his
trainer is killed. Holmes exploits a negative inference (IG is Inspector Gregory of Scotland Yard):
IG: "Is there any other point to which you would wish to draw my attention?" SH: "To the curious incident of the dog in the night-time."
IG: "The dog did nothing in the night-time."   SH: "That was the curious incident"
Holmes reasons that because the dog did not bark in the night it knew whoever was moving Silver Blaze.
Of note is that Silver Blaze also contains a quick calculation problem by Holmes where he counts the number of telegraph posts being passed
by the train conveying Dr. Watson and himself. The posts are 60 yards apart and Holmes reckons the velocity at 53.5 miles per hour: 

We had left Reading far behind us before he thrust the last of the newspapers under the seat and offered me his cigar-case.

"We are going well," said he, looking out of the window and glancing at his watch. "Our rate at present is fifty-three and a half miles an hour."

"I have not observed the quarter-mile posts," said I.

"Nor have I. But the telegraph posts upon this line are sixty yards apart, and the calculation is a simple one."

 Either Holmes has a phenomenally accurate watch or something is wrong here. 
© 2018 Peter F. Zoll. All rights reserved.
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