barm

And then you may work it with barm if you please; but it is most commended without.

When it is cold, set it together with some barm, as you do Beer.

When it is cold, put a little barm to it, and let it work like Beer.

Then Tun it up, and put Barm to it, that it may ferment well.

The yeast added to the worts as a ferment, ought to be the best top barm of the London porter breweries.