ABSTRACT
In the course of Chapter Seven it was shown how, towards 7 to 8 years, an accurate conception was formed of speed to the extent that concrete operations were involved: different distances travelled in equal times or equal lengths in unequal times, the movements to be compared being always wholly or partly perceived at the same time. But two questions remain to be discussed, which immediately follow on from the foregoing ones. What happens when, instead of perceiving both movements at the same time, the child can then only see them one after the other (except of course by recording the given factors in drawing or writing): will the need for this comparison in succession which is no longer directly perceptual simply delay the solution, by requiring more work of the child, or will it cause the reappearance of methods of reasoning already outgrown on the preceding level? On the other hand, how skilful will the child be in comparing unequal distances covered in unequal times? In other words what will be the structure of the extensive operations (proportion) and the metrical operations necessary in solving these new problems?
