The difficulty of having changes made in existing alphabets is very great, yet this is not necessarily a disadvantage. Much insight into the origin and gradual improvements of sets of letters has been gained by studying the order in which the several letters stand. The order varies greatly in different nations, and varies slightly at different epochs in the same nation. In taking the Ph[oe]nician letters, the Greeks dropped some, used others for slightly different sounds, and added a few to express sounds that were important to them or that did not exist in the Ph[oe]nician. But this was done very gradually. It never has been easy to induce people to change and improve their alphabets. But there is another reason why men have refused to change the order of letters by inserting a new and useful letter in the place where it naturally belonged. The Greeks and many other peoples used the letters of the alphabet for numerals. We use our own numbers without stopping to think whence they came. The cumbersome system used by the Romans, and called after them, consisted of strokes (I-II-III-IIII) to indicate the four fingers, and two strokes joined (V) to represent the hand, or five fingers. Ten was a picture of two hands, or two V's (X). Among the Etruscans the half of one, or, as we put it, 1/2 was >, which we think stood for a forefinger crooked in order to denote the half of one finger. But when the Etruscans and Greeks worked at the higher mathematics or attempted hard sums in arithmetic, they are much more likely to have used letters, in order to avoid the clumsiness of these numerals; in other words, they used what looked like a kind of algebra. We know that they tried to simplify the Roman numerals at Rome by making four and nine with three strokes instead of four, by placing an I before the V and an I before the X (IV and IX).