We are now in a position to approach the last stage in our task, that which deals with the growth and development of various weight-standards, all of which start from a common unit. Of necessity Egypt, Babylon, Greece and Italy will claim a chief share of our attention. The question now is, Shall we deal with these regions according to the priority of their civilization, that is, in the order in which I have just named them, or shall we rather adhere to the principle which has hitherto guided us, of working back from that which is better known to that which is less known?
On the whole the former is perhaps the better for our present purpose. As we believe that we have discovered by the inductive method the common unit which lies at the base of all these systems, there is no longer the same necessity for always starting with that which is the less ancient. Besides, if we were nominally to pursue this course, it by no means follows that we would be starting from that which is the best known. Prima facie we ought to start with the Roman system, the tradition of which has remained unbroken down to our own days. We could work back through the system of the Middle Ages to the time of Constantine the Great, from Constantine to the early Empire, and from the Empire to the Republic. Moreover no weight-unit is more accurately known than the Roman pound. But the early history of Rome is so obscure