The Subject Matter of Geometry. In geometry, although we shall continue the use of arithmetic and algebra, our main work will be a study of what will later be defined (" 13) as geometric figures. The student is already familiar with the physical objects about him, such as a ball or a block of wood. By a careful study of the following exercise, he may be led to see the relation of such physical solids to the geometric figures with which he must become familiar. hat will the surfaces of the block generate ? all of them ? Can you move a surface so that it will not generate a solid ? Yes, by moving it along itself. What will the edges of the block generate ? Can you move an edge so that it will not generate a surface ? What will the corners generate ? Can you move a point so that it will not generate a line ?