Seems silly to me, if it's a bay, there's silt flowing into it, time itself could pile 10cm of detritus into the deepest parts and make it more shallow.
That's the whole point. 100 phatoms is really imprecise. But on translation, they didn't bother keeping the significant digit count equal, and since 182.8 m= 100 f , they just left it like that. I mean, it's the only reason he could guess there was a unit change...
Or currents might deepen a hole too. Putting silt in one place can cause other places to change too.
And if it were more shallow, shipping would have a big impact too.
100 phantoms
So, there's a Department of Homeland Security sign near the parking lot at the ferry.
Speed Limit 4 1/2 Miles Per Hour.
I always thought that was stupid.
Then I saw this comic and realized it must have been in KPH originally.
So I translated it myself.
7.242 KPH.
Do speedometers even measure such low speeds with anywhere near that precision?
If you've 24" tyres and a first gear ratio of 3.5:1, then:
RPM x (pi x 24" circumference )x (1/63360 miles per inch) x (60 minutes per hour) x (1/3.5 ratio) = 4.5 mph
Giving the RPM at a satisfyingly round 221.6 rpm.
I think they sometimes do that just to get people’s attention. You don’t normally see fractional speed limits so you pay more attention.
But you see 5 mph signs all over. It's in a parking lot, so it's still redundant.
xkcd
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