The difference between these two papers, both consisting, as they do, of pure esparto with a small proportion of ash may be emphasised by comparing the analysis by _weight_ with analysis by _volume_. The two papers in question when analysed by weight proved to have the following composition:-- -------------------------------------------- | Parts by Weight. +----------------+------------ -- | Featherweight. | Ordinary. --------------+----------------+------------ Esparto fibre | 96·0 | 95·4 Ash, etc | 4·0 | 4·6 | ----- | ----- | 100·0 | 100·0 --------------+----------------+------------ But if the papers are compared in terms of the _composition by volume_, it will be found that the featherweight contains a large amount of air space. --------------+----------------------------- | Composition by Volume. +----------------+------------ -- | Featherweight. | Ordinary. --------------+----------------+------------ Esparto fibre | 28·0 | 65·5 Ash, etc | 0·7 | 1·8 Air space | 71·3 | 32·7 | ----- | ----- | 100·0 | 100·0 --------------+----------------+------------ In other words, the conditions of manufacture for the bulky paper are such that the fibres are as far apart from one another as possible, and the cohesion of fibre to fibre is reduced to a minimum. While paper of this description is agreeable to the printer, and probably to the general reading public, yet its strength and physical qualities, from the point of view of resistance to wear and tear, are of the lowest order. It is very difficult to rebind books made from it, which is not altogether to be wondered at, seeing that the bookbinder's stitches can hardly be expected to hold together sheets containing 60 to 70 per cent. of air space. This concrete case emphasises the necessity for including in a schedule of standards of quality a classification of papers according to strength and bulk. _Surface._--The introduction of new methods of printing has brought about some changes in the process of glazing and finishing paper which are not altogether favourable to the manufacture of a sheet having maximum qualities of strength and elasticity, two conditions which are essential to permanence. In other words, the very high finish and surface imparted to paper by plate-glazing, supercalendering, water finish, and other devices of a similar character is carried to excess.