Many of these lines of evolution in the methods of manufacture have been previously discussed in their appropriate sections. They may all be summarized as attempts at more economical production. Prominent amongst them is the persistent effort to attain quicker processes. During the last twenty-five years the time necessary to produce the heavy leathers has been reduced from 12 months to as many weeks. The tendency is to reduce the time further still, but this is of course increasingly difficult to accomplish. On the other hand, it is more urgent to strive in this direction than ever, because a needless week involves more capital lying idle than ever before. Moreover, as most leather factories are now large works, a saving even of 24 hours has become a serious item in economic production. Hence in liming, bating, tanning, drying and in warehousing there are increased efforts to make a quicker turnover. A good illustration of this "speeding up" in modern tanneries is the adoption by all large factories of much more rapid methods of extracting tannin. On the old press-leach system liquors may be percolating through the material for possibly a fortnight. The extract manufacturer reduces this operation to about two days. Steam generated from the spent bark is used to heat the extracting vats, and to work a vacuum pan or evaporator whereby more water can be used and a more complete as well as a more rapid extraction obtained. The evaporator also makes easy the preparation of the strong liquors used in modern tanning. Hand-in-hand with quicker production and manipulation are the attempts to obtain a larger turnover. It is realized that the big business attains cheap production. Even before the war the smaller factories were disappearing. A small tannery must now either extend or close down. This has been better realized in the heavy than in the light leather trades. In the sole leather tanneries very often many thousand hides per week are put into work, but in the glacé kid factories there is nothing yet to correspond to the output of American glacé factories, which sometimes reaches three or four thousand dozen a day.