9. This figure two (2) is part of the Language of Arithmetic.
10. In this picture one boy is sitting, playing a flageolet. What is the other boy doing? If the boy standing should sit down by the other, how many boys would be sitting together? One boy and one other boy are how many boys?
11. You see a flageolet and a violin. They are musical instruments. One musical instrument and one other musical instrument are how many?
12. I will write thus: 1 1 2. We say that 1 boy and 1 other boy, counted together, are 2 boys; or are equal to 2 boys. We will now write something to show that the first 1 and the other 1 are to be counted together.
13. We name a line drawn thus,—, a horizontal line. Draw such a line. Name it.
14. A line drawn thus, | , we name a vertical line. Draw such a line. Name it.
15. Now I will put two such lines together; thus, +. What kind of a line do we name the first (—)? And what do we name the last? (|)? Are these lines long or short? Where do they cross each other?
16. Each of you write thus: —, | , +.
17. This, +, is named Plus. Plus means more; and + also means more.