The square of any number is the result obtained by multiplying that number by itself.

The square root of any number is that number which, when multiplied by itself, will produce the given number.

When the slide is shut so that 1 on the line C is even with 1 on the line D, then the square of any number on the line D is found just above it on the line C: thus the square of 3 on the line D is 9, which is found just above it on the line C; and the square root of any number on the line C is found just below it on the line D: thus the square root of 9 on the line C is 3, which is found just below it on the line D. The square root of 5 on the line C is 2.23 (2 23/100), which is found just below it on the line D.