digits, but not as regards the
, that one comes first which has either no
digit or a smaller one than the other. This rule of arrangement, as the reader can easily convince himself, gives rise to a compact series containing all the integers not divisible by 10; and, as we saw, there is no difficulty about including those that are divisible by 10. It follows from this example that it is possible to construct compact series having
terms. In fact, we have already seen that there are
ratios, and ratios in order of magnitude form a compact series; thus we have here another example. We shall resume this topic in the next chapter.