OMG!!
Thankyou guys (both male and female)!
And with this information I have discovered something else (bit like re-inventing the wheel i suppose!).
I was wondering how they knew where to put the various numbers on the circle. Well if you put the "10" and think of it as a 1 at the top (or 12 O'Clock position)...
Log1 = 0
So you don't have to move the wheel at all. 1 is right there in front of you.
Log10 = 1
So if you want to find 10 you have to turn the wheel around once.
Log17.8 = 1.25
So if you want to find 17.8 you have to turn the wheel around one and a quarter times Anti-clockwise. (or look at the 3 O'Clock position.)
Log31.7 = 1.5
So if you want to find 31.7 you have to turn the wheel around one and a half times anti-clockwise.( or look at the 6 O'Clock position.)
Log56.5 = 1.75
So if you want to find 56.5 you have to turn the wheel around one and three quarters times anti-clockwise.(or look at the 9 O'Clock position.)
Log0.1 = -1
So to find 0.1 you have to turn the wheel around once clockwise.
Log 3.17 = 0.5 so to find 3.7 you have to turn the wheel around just half a turn anti-clockwise.
Log3170 = 3.5 so to find 3170 you have to turn the wheel around anti-clockwise three and a half times.
Brilliant!!!
