As stated, this is one way of finding out the size of an old book; but there is another way--by means of the "signatures," which consist of small letters or figures at the foot of the page of nearly every book. The leaves (not pages) must be counted between signature and signature, and then if there are two leaves the book is a folio, if four a 4to, if eight an 8vo, if twelve a 12mo, if sixteen a 16mo, and if thirty-two a 32mo. Take, as an example, this very book you hold in your hand, and it will be found that there are eight leaves between signature and signature; hence it is an 8vo, though a small one, owing, of course, to the small size of the paper from which it has been made, _viz._, crown. Had it been a little smaller (still preserving its oblong shape) it would have been a foolscap 8vo, if somewhat larger a demy 8vo, if larger still a royal 8vo, and largest of all imperial 8vo. The quartos and folios are governed by identical rules, and hence in the trade the sizes of books are very numerous. Simple as this method of computation may appear, a great deal of controversy has taken place on the subject--so much so, indeed, that there are people to be found who stoutly maintain, and adduce proof to show, that what looks like a 4to is in reality an 8vo, or _vice versa_. It would be out of place to enter into a discussion of this nature, and, therefore, I should advise the young collector to count the leaves between signature and signature, and to abide by the result, regardless of all the learned arguments of specialists. If there are no signatures, and the book is an old one, then study the position of the water-mark. As examples, it will be sufficient to note that the _Illustrated London News_ is folio, _Punch_ is 4to, and the _Cornhill_ and nearly all the monthly magazines are large 8vos. There is a large number of varieties of each size, but on the whole books which approximate to the sizes of magazines are of the sizes named. Occasionally in judging by the eye in this manner a mistake may be made; but of one thing there is no doubt, that a vast amount of argument would have to be expended upon the subject before the judgment could be proved to be wrong. Paper-makers at one period made their sheets in frames of a given size, so that it was a comparatively easy matter to distinguish the size of a book at a glance. Now-a-days, however, there appears to be but little uniformity in this respect, and the difficulty is consequently considerably increased. The following measurements will, however, be found approximately correct, and they may be utilised in a practical manner by taking a sheet of brown paper of the required size and folding it as previously mentioned, thus forming crown 8vos, crown 4tos, elephant folios, &c., at will. The practice is good, and it will not need to be often repeated.