Single Stroke Vertical Lower Case Letters
Words lettered in lower case or “small” letters are easier to read than when made in capital letters. These letters are made with bodies two-thirds the height of the capitals, the ascenders (b, d, f, etc.) extending up to the cap line and the descenders (g, p, q, etc.) dropping the same distance below.
Thomas E. French and Carl L. Svensen Mechanical Drawing For High Schools (New York: McGraw-Hill Book Company, Inc. , 1919) 16