Sentence:  There is a Law among them that whoſoever beats one of thoſe Clerks ſo, that his Cap fall to the ground, he is liable to a very ſevere penalty (if I well remember to looſe his hand) which nevertheleſs happens frequently in the "Cabac": but to prevent the worſt when a Layman is minded to beat one of thoſe Muſhrooms, he firſt takes off his Cap and then <WSD>trounces</WSD> him off ſo long as he will, which done he ſets the Cap upon the right Block again. 
Meaning of the word marked with <WSD> tags:  To beat severely; to thrash.