Cone-shaped graduates are not actually equally spaced. The reason for this is because the volume of a cone is not directly proportional to its height. In other words, the volume of a cone does not increase at a constant rate as the height increases. This is because the base of a cone is a circle, and the area of a circle increases at a faster rate than its height. As a result, the cone-shaped graduate must be marked with unevenly spaced lines in order to accurately measure volumes.