EXERCISE 24
Man has been storing up useful knowledge about himself and the universe at the rate which has been spiraling upward for 10000 years.
The __1_ took a sharp upward leap with the invention of writing,but even __2_ it remained painfully slow for several centuries.The next great leap forward __3_ knowledge acquisition did not occur __4_ the invention of movable type in the 15th century by Gutenberg and others.__5_ to 1500,by the most optimistic __6_,Europ was producing books at a rate of 1000 titles per year.This means that it __7_ a full century to produce a library of 100000 titles.By 1950,four and a half __8_later,the rate had accelerated so sharply that Europe was producing 120000 ttitles a year._9_ once took a century now took only ten months.By 1960,a __10_ decade later,the rate had made another significant jump,__11_ a century's work could be finished in seven and a half months.__12_,by the mid-sixties,the output of books on a world__13_,Europe included,approached the prodigious figure of 900 titles per day.
One can __14_ argue that every book is a net gain for the advancement of knowledge.Nevertheless we find that the accelerative __15_ in book publication does,in fact,crudely __16_ the rate at which man discovered new knowledge.For example,prior to Gutenberg __17_ 11 chemical elements were known.Antimony the 12th,was discovered __18_ the time he was working on his invention.It was fully 200 years since the 11th,arsenic,had been discovered.__19_ the same rate of discovery contioned,we could by now have added only two or three additional elements to the periodic table since Gutenberg.__20_,in the 450 years after the time,certain people discovered some seventy additional elements.And since 1900 we have been isolating the remaining elements not a rate of one every two centuries,but of one every three years.
1) A accumulation B development C knowledge D rate
2) A so B if C then D when
