More from A Study in Scarlet.

“the base of a beetling crag”
This use of beetlng puzzled me, so I looked it up. Here, it means overhanging.
But why?
Sez etymonline:

beetle (v.)
“project, overhang,” c.1600, back formation from bitelbrouwed “grim-browed, sullen” (mid-14c.), from bitel “sharp-edged, sharp” (c.1200), probably a compound from O.E. *bitol “biting, sharp,” related to bite, + brow, which in Middle English meant “eyebrow,” not “forehead.” Meaning “to overhang dangerously” (of cliffs, etc.) is from c.1600.

“their course lay through intricate defiles”
defiles: narrow passages.

“there to recruit his health”
recruit: strengthen

“There are swift- flowing rivers which dash through jagged cañons”
Doyle is describing a large area to the east of the Rockies. Interesting that he should use the Spanish word.

Much of the story concerns the Mormons. Brigham Young makes an appearance. One of the sentences Doyle puts into his mouth is, “We Elders have many heifers[1], but our children must also be provided.”
The footnote for [1] is:
“Heber C. Kemball, in one of his sermons alludes to his hundred wives under this endearing epithet.”
I would also mention that, in my dialect at least, it would be normal to say “our children must also be provided for”, rather than “provided”, in such a sentence.

EDIT: fixed up my bolding

From: The proverbs Epigrams and Miscellanies of John Heywood, edited by John S. Farmer, London, 1906, in The first Hundred of Epigrams Invented and Made by John Heywood, Londini, 1592, p. 142 [Farmer] [link here]:

[link to the above image, here]

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Also, from the same work [Farmer], on p. 52 [link here]:

[link to the above image, here]

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This seems to me to be a figure of speech derived from comparing the aspect of a person’s brow and eyes to the ‘brow’ and eyes of a beetle.

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Again, etymonline offers, for “beetle (v.)”:

beetle (v.)
“project, overhang,” c.1600, back formation from bitelbrouwed “grim-browed, sullen” (mid-14c.), from bitel “sharp-edged, sharp” (c.1200), probably a compound from O.E. *bitol “biting, sharp,” related to bite, + brow, which in Middle English meant “eyebrow,” not “forehead.” Meaning “to overhang dangerously” (of cliffs, etc.) is from c.1600.

I gather from these posts that “beetle-browed” isn’t as familiar to other English speakers as it is to us in the UK.  OED:

Forms:  In beetle brows, beetle-browed. Forms; ME bitel, bytel(l, ME betyl, bittil, 15 beetell, beetill, beetyll, 16 betle, bittle, 15– beetle.(Show Less)

Etymology:  Found first in the comb. beetle-browed (1362); much later (1532), beetle is treated as a separate word in beetle brow(s ; whence a derived verb to beetle v.1 (see beetle n.1) formed by Shakespeare.
(As the 14–15th cent. form had bitel- , bytel- , it has been proposed to identify it with bitel adj. ‘biting, cutting like a sharp-edged tool,’ used by Ormin and Layamon, which is phonetically possible: but, beside the hardly satisfactory sense, there is the difficulty that bitel appears to have been obsolete for 160 years when the first example of bitel-brouwed occurs. It is more likely that the word here is one of the two ns. beetle n.1, both extant in 14th cent., and both having the form bitel. The choice depends largely upon the exact meaning originally attached to ‘beetle-browed,’ which was a reproachful epithet, and appears to have referred to the shaggy prominence of the eye-brows. (Brow in Middle English was always = eyebrow, not = forehead.) It is probable therefore (as suggested by Dr. F. Chance) that the comparison is to the short tufted antennæ of some species of beetles, projecting at right angles to the head, which may have been called ‘eyebrows’ in English as well as in French; for in French the expression sourcils de hanneton ‘cockchafers’ eyebrows’ is the name given to a species of fringe made in imitation of the antennæ of these insects.)

A type of mallet has been called a beetle from the ninth century to date.

The origin of “beetle” (the insect) is apparently from the Old English verb bitul/ol and bitan, meaning bite.

Shakespeare introduced me to beetle in my youth, as he did to so much else.

What if it tempt you toward the flood, my lord,
Or to the dreadful summit of the cliff
That beetles o’er his base into the sea,

Hamlet, I,iv

I was familiar with the term beetle-browed, but not with the verb beetle=overhang.

I think “beetle-browed” is pretty well known in the US.

ElizaD - 24 November 2012 12:45 PM

I gather from these posts that “beetle-browed” isn’t as familiar to other English speakers as it is to us in the UK.  OED:

Forms:  In beetle brows, beetle-browed. Forms; ME bitel, bytel(l, ME betyl, bittil, 15 beetell, beetill, beetyll, 16 betle, bittle, 15– beetle.(Show Less)

…

A type of mallet has been called a beetle from the ninth century to date.

The origin of “beetle” (the insect) is apparently from the Old English verb bitul/ol and bitan, meaning bite.

We had a thread that mentioned betel “hammer, mallet” a little over a year ago:

http://www.wordorigins.org/index.php/forums/viewthread/3286/

Thanks for pointing me to SL’s great links.

Dr. Techie - 24 November 2012 06:51 PM

I think “beetle-browed” is pretty well known in the US.

I agree.  I think that if we were asked “What’s beetle about it?” precious few would have any sort of rational answer, but we are familiar enough with the expression’

EDIT: Well, that worked a treat.

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Good point.

some strychnine-like substance which would produce tetanus”

I was not previously familiar with this usage of “tetanus”, meaning extreme muscular contraction generally: I would have taken tetanus to be specifically a condition caused by C. tetani. Apparently the usage above is still in use.

Knock old Sherman up

Holmes means “wake old Sherman up by knocking”.

EDIT: fixing my italics before they fix me

The difference between the British and American definitions of knock up are well documented and a staple of linguistic comedy.

In modern American medical English, at least, the more usual term for extreme uncontrollable muscular contraction not caused by Clostridium tetani would be “tetany” or “tetanic contraction”. This sense of “tetanus” is still listed in medical dictionaries but I think it’s pretty much obsolete, due to the danger of confusion (treatment for drug-induced or hypocalcemic tetany and clostridial tetanus being rather different).