NavList:

I don’t recall the ‘bar one’ notation for logs of numbers less than unity ever being a problem at school, at Imperial College, or on the RAF Staff Navigator and Aerosystems Courses.  This was probably because I wasn’t required think about it, simply to do as I was told.  What did worry me was when I found a ‘sailings’ calculation of my father’s using logs beginning with 9 point (the only example I have of his navigational prowess unfortunately).  Frank kindly explained and it was soon clear.  Moreover, it’s practicality becomes clear if you use an old enough copy of Nories.  My eBay 1969 copy uses only 9s.  My 50p charity shop 1991 edition offers a choice of both bar ones and nines.

I suppose if I had to try to explain it to a beginner, I’d say “It’s a bit like starting off by making the smallest number you’re ever likely to meet, e.g. nought point nine noughts one, greater than one by multiplying everything by 10 to the power of ten.   Then at the end, divide your answer by 10 to the power of 10, but it’s all done in log notation”.  Neat, plausible, and probably wrong like most simple explanations, e.g. like many explanations of the lift from a three-dimensional aircraft wing on a two-dimensional textbook page, but it does the trick for the time being.

The other thing which I have difficulty with is when Professor Google uses posh words like ‘integer’ and ‘mantissa’, which I’ve long ago forgotten the meaning of, so that I’m immediately sent into ‘glossary chase’ before I can even start learning what I’m really looking for.  Why doesn’t he just say ‘the bit at the front’ and’ the bit at the back’.  Neat, plausible, and not always true, but it would suit for the occasion.  DaveP (P.S. Yes I am aware that you encounter integers much higher and lower than nine point in the ‘logs of trig fns’ tables.)