Other things being equal, make distinctions by the clearest method, fit material to the tendency of the eye to see an 'eyeful' at a time (roughly 1-1/2 inch by 1/2 inch in a book; 1-1/2 ft. by 1/2 ft. on the blackboard), and let one picture teach only one fact or relation, or such facts and relations as do not interfere in perception. The general conditions of seating, illumination, paper, and the like are even more important when the eyes are used with numbers than when they are used with words. [Illustration: FIG. 42.--Try to count the rungs on the ladder, or the shocks in the wagon.] [Illustration: FIG. 43.--How many oars do you see? How many birds? How many fish?] [Illustration: FIG. 44.--Count the birds in each of the three flocks of birds.] [Illustration: FIG. 45.--Note the lack of clear division of the hundreds. Consider the difficulty of counting one of these columns of dots.] [Illustration: FIG. 46.--What do you suppose these pictures are intended to show?] [Illustration: FIG. 47.--Would a beginner know that after THIRTEEN he was to switch around and begin at the other end? Could you read the SIX of TWENTY-SIX if you did not already know what it ought to be? What meaning would all the brackets have for a little child in grade 2? Does this picture illustrate or obfuscate?] [Illustration: FIG. 48.--How long did it take you to find out what these pictures mean?] [Illustration: FIG. 49.--Count the figures in the first row, using your eyes alone; have some one make lines of 10, 11, 12, 13, and more repetitions of this figure spaced closely as here. Count 20 or 30 such lines, using the eye unaided by fingers, pencil, etc. ] [Illustration: FIG. 50.--Can you answer the question without measuring? Could a child of seven or eight?] [Illustration: FIG. 51.--What are these drawings intended to show? Why do they show the facts only obscurely and dubiously?] [Illustration: FIG. 52.--What are these drawings intended to show? What simple change would make them show the facts much more clearly?] [Illustration: FIG. 53.--Arranged in convenient "eye-fulls."] [Illustration: FIG. 54.--Clear, simple, and easy of comparison.] [Illustration: FIG. 55.--Clear, simple, and well spaced.] [Illustration: FIG. 56.--Well arranged, though a little wider spacing between the squares would make it even better.] THE USE OF CONCRETE OBJECTS IN ARITHMETIC