Though this doesn't sound like a decoction mash.
"It is first crushed by passing between a series of large rollers, and next is transferred to the mash-tubs, where it is stirred about with water at 120° to 140° Fahr., and boiling is then gradually added until all is heated to about 170° Fahr. The infusion or wort is allowed to stand until the suspended matters have settled, when it is drawn off, and a second wort is obtained by treating the residuum with hot water. The first wort is boiled with the hops, the second wort is then let in, and the whole is boiled for about four hours. It is then run into the cooler, where it is quickly chilled to between and 50° Fahr., by running over small pipes through which cold water is continually flowing."
Holmes' Brewing Trade Gazette - Thursday 01 September 1881, page 15.
What sounds like doughing in was at 50º C. But, as boiling water is added, rather than boiling part of the mash, it's quite different to a decoction mash. And more like a sort of step infusion mash. I'm guessing that they had modified the mashing process in the USA to make it more efficient. And cheaper.
"As soon as it is properly cooled it is run into the fermenting tuns, where it is mixed with one gallon of yeast for every twenty to twenty-five barrels. Fermentation continues for about twenty days. At first there is a heavy froth, which soon subsides, however, leaving the surface clear. At the end of this period it is racked off into hogsheads, the yeast remaining at the bottom of the tuns. These hogsheads are allowed to Stand with the bungs open until a few days before the beer is put into barrels for use, when the bungs are driven in to accumulate carbonic acid for life."
Holmes' Brewing Trade Gazette - Thursday 01 September 1881, pages 15 - 16.
A hogshead is pretty small for a lagering vessels. I have seen ones of around that size, but was in Brauerei Schmidt, one of the, if not the, smallest production breweries in Germany. The bunging period seems a bit short at "a few days". Though it must have been sufficient to carbonate the beer. I know from other sources that American beer was pretty heavily conditioned in the late 10th century.
I'd love to accumulate carbonic acid for life. Any idea wher I can load up?