Sentence:  [M]ost threshing-machines are defective in regard to separating the awns of barley from the grains, especially when it has been led home in a raw or soft state. Various devices are often had recourse to for obviating this defect. ... In other cases, where either of these devices are wanting, it has to be <WSD>hummelled</WSD> on the barn-floor, either by means of threshing with the old flails or swiples, or by stamping it with an implement resembling a paviour's ram, the under end of which is armed with plate iron made like a honeycomb. On some occasions, barley has known to be too much <WSD>hummelled</WSD>, at least for the use of maltsters; as, when the awn breaks off so close as to leave a small portion of the kernel naked, such grains do not malt kindly. 
Meaning of the word marked with <WSD> tags:  To separate (barley, oats, etc.) from the awns.