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As you might already have guessed, I've been searching for Anton Dreher in Google Books again. This time it turned up something more fascinating than awestruck tales of the scale of his enterprise. In fact it's hardly anything to do with Dreher at all.

The little table embedded in this text tells a more telling tale. One of the swift change from top- to bottom-fermentation in 19th century Bohemia. It was the start of the Lager boom which still hasn't quite petered out.

"For beer, moreover, the question of temperature is one of supreme importance; indeed the recognised influence of temperature is causing on the continent of Europe a complete revolution in the manufacture of beer. When I was a student in Berlin, in 1851, there were certain places specially devoted to the sale of Bavarian beer, which was then making its way into public favour. This beer is prepared by what is called the process of low fermentation ; the name being given partly because the yeast of the beer, instead of rising to the top and issuing through the bunghole, falls to the bottom of the cask ; but partly, also, because it is produced at a low temperature. The other and older process, called high fermentation, is far more handy, expeditious, and cheap. In high fermentation eight days suffice for the production of the beer; in low fermentation, ten, fifteen, even twenty days are found necessary. Yast quantities of ice, moreover, are consumed in the process of low fermentation. In the single brewery of Dreher, of Vienna, a hundred million pounds of ice are consumed annually in cooling the wort and beer. Notwithstanding these obvious and weighty drawbacks, the low fermentation is rapidly displacing the high upon the continent. Here are some statistics which show the number of breweries of both kinds existing, in Bohemia in 1860, 1865, and 1870 :—

High Fermentation
Low Fermentation

Thus in ten years the number of high-fermentation breweries fell from 281 to 18, while the number of low-fermentation breweries rose from 135 to 831. The sole reason for this vast change—a change which involves a greater expenditure of time, labour, and money—is the additional command which it gives the brewer over the fortuitous ferments of disease. These ferments, which, it is to be remembered, are living organisms, have their activity suspended by temperatures below 10º C., and as long as they are reduced to torpor the beer remains untainted by either acidity or putrefaction. The beer of low fermentation is brewed in winter, and kept in cool cellars; the brewer being thus able to dispose of it at his leisure, instead of forcing its consumption to avoid the loss involved in its alteration if kept too long. "
"The Fortnightly, Volume 26" edited by John Morley, 1876, pages 561-562.
That's a pretty rapid change. In a single decade top-fermentation all but disappeared.