Imperial Leather Trade, should this be necessary. French chestnut extract, and quebracho extract, however, are much too valuable tanning materials to exclude for merely sentimental reasons. These instances indicate possible advantages in Imperial co-operation, but also show the need for caution in the elaboration of such schemes. Although a partial, and indeed increasing, measure of State Control is probable, there has been as yet no serious proposal to nationalize the leather industry. Such a proposition, indeed, is hardly ripe even for discussion. Until the nationalization of transport and of mines is a proved success, and until the merely distributive undertakings of the municipalities (_e.g._ of coal and of milk and other foods) are past the experimental stage, any proposition to nationalize the leather trades seems premature. It is noteworthy, however, that in Queensland, Australia, the Government have the right to commence and to administer State Tanneries. Any progress in the direction either of democratization or of nationalization, has been certainly postponed by the sudden and unprecedented trade slump which commenced in the earlier part of 1920. This depression, in spite of heavy falls in the prices of raw materials, has made economic production a much more difficult problem. It has undoubtedly given a further stimulus to evolution towards the trust type, and created a further tendency towards the closing of the smaller factories, and the employment of labour-saving devices. When the general fall in prices has made an appreciable fall in the cost of living, some reduction in the leather workers' wages, together with more efficient work, will also contribute to the solution of the difficulty. It is chiefly to be desired, however, that the export trade should be restored. The realization of this hope depends largely upon the establishment of peace and prosperity abroad, and the consequent stabilization of the various foreign exchanges. PART V.--GELATINE AND GLUE. SECTION I.--PROPERTIES OF GELATINE AND GLUE Many of the chemical properties of gelatine, especially those which distinguish it from other proteins, have been described in the Introduction to this volume, and need no further comment. In this section its colloid nature and behaviour will chiefly be considered, for these points have greatest importance from the standpoint of industrial chemistry. It is hoped, moreover, that this section will be of interest not only to the chemist concerned in the manufacture of gelatine and glue, but that it will be of value also to those concerned in leather manufacture. The difference between the "collagen" which composes the hide fibre and the high-grade gelatines is so small that for many practical purposes it may be considered negligible. Thus the description of the behaviour of a gelatine gel is very largely applicable to a hide gel also.