Sentence:  The outside <WSD>bout</WSD> of each land is ploughed two inches deeper, and from thence the water runs into cross furrows, which are dug with a spade ... I have an instrument of great power, called a scarifier, for this purpose. It is drawn by four horses, and completely prepares the land for the seed at each <WSD>bout</WSD>. 
Meaning of the word marked with <WSD> tags:  The going and returning of a plough, or other implement used to mark the ground and create a headland, across a field.