But it is now time to return from this long digression, into which I have been insensibly led, in endeavouring to explain the reasons why the exchange between the countries which pay in what is called bank money, and those which pay in common currency, should generally appear to be in favour of the former, and against the latter.

The great importance of this subject must justify the length of the digression.

The advantage of this is that he is enabled to make use of Don Quixote as a mouthpiece for his own reflections, and so, without seeming to digress, allow himself the relief of digression when he requires it, as freely as in a commonplace book.

Let me now beg pardon for this digression, and return to my subject by proposing some practicable methods for regulating of servants, which, whether they are followed or not, yet, if they afford matter of improvement and speculation, will answer the height of my expectation, and I will be the first who shall approve of whatever improvements are made from this small beginning.

That is the idea which Felix Aderca places at the root of his spectacular digression".

The third law, which shows a constant proportionality between the cube of the semi-major axis of a planet's orbit and the square of the time of its orbital period, is set out in Chapter 5 of this book, immediately after a long digression on astrology.