"N"
Scales (also known as decilog scales) 

N_{1} 
The N_{1} scale is a decimal loglog
scale that is available only on the bottom rule, in the
bottom 4 slots for scales. It runs from 1.0023 to
1.0232. Formula: N_{1} = 10^{0.001x} 
N_{2}  The N_{2} scale is a decimal loglog
scale that is available only on the bottom rule, in the
bottom 4 slots for scales. It runs from 1.0234 to
1.258. Formula: N_{2} = 10^{0.01x} 
N_{3}  The N_{3} scale is a decimal loglog
scale that is available only on the bottom rule, in the
bottom 4 slots for scales. It runs from 1.26 to 10.0. Formula: N_{3} = 10^{0.1x} 
N_{4}  The N_{4} scale is a decimal loglog
scale that is available only on the bottom rule, in the
bottom 4 slots for scales. It runs from 10.0 to 10^{10} Formula: N_{4} = 10^{x} 
1/N_{1} 
The 1/N_{1} scale is a decimal
loglog scale that is available only on the top rule, in the
top 4 slots for scales. It runs from 0.9977 to 0.977
running left to right. Formula: 1/N_{1} = 10^{x} 
1/N_{2}  The 1/N_{2} scale is a decimal
loglog scale that is available only on the top rule, in the
top 4 slots for scales. It runs from 0.977 to 0.794
running left to right. Formula: 1/N_{2} = 10^{0.1x} 
1/N_{3}  The 1/N_{3} scale is a decimal
loglog scale that is available only on the top rule, in the
top 4 slots for scales. It runs from 0.794 to 0.1
running left to right. Formula: 1/N_{3} = 10^{0.01x} 
1/N_{4}  The 1/N_{4} scale is a decimal
loglog scale that is available only on the top rule, in the
top 4 slots for scales. It runs from 0.1 to 10^{10}
running left to right. Formula: 1/N_{4} = 10^{0.001x} 