The rate at which man has been storing up useful knowledge about himself and the universe

has been spiraling upward for 10,000 years. The rate t【66】a sharp upward leap thousands of years ago, w【67】the invention of writing, but even so it remained painfully slow o【68】centuries of time. In knowledge-【69】(acquire) the next great leap forward did not occur until the invention of movable type in the fifteenth century by Gutenberg and others. Prior【70】1500, by the most optimistic est【71】, Europe was producing books at a rate of 1, 000 titles per year. This means that it would take a full century to produce a library of 100,000 titles. The rate had ac【72】so sharply by 1950, four and a half centuries later,【73】Europe was producing 120,000 titles a year.【74】once took a century now took only ten months. By 1960, a s【75】decade later, the rate had made another significant jump, so that a century's work could be completed in seven and a half months. And, the output of books【76】a world scale by the mid sixties, Europe【77】(include) , approached the remarkable figure of

1,000 titles per day.

One can hardly argue that every book is a net gain for the advancement of knowledge. Nevertheless, we find that the increase in book publication does, in fact, crudely para【78】the rate at which man discovered new knowledge. For example, before Gutenberg only 1 chemical dements were known. Antimony (锑), the 12th, was discovered at about the time he was working on his invention. It was fully 200 years s【79】the 11th, arsenic (砷), had been discovered. Had the stone rate of discovery continued, we would by now have added only two or three additional dements to the periodic table since Gutenberg. In【80】, in the 450 years after his time, some seventy additional elements were discovered. And since 1900 we have been isolating the remaining elements not at a rate of one every two centuries, but of one every three years.

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