Note 1: (gipsies)
While this word is most often used to refer to the nomadic Romany people, believed to be descended from those who left India in a series of migrations, this may here be referring only to a band of "travellers", who live a similar nomadic lifestyle, but who do not have the Romany ethnicity. The Romany population is more concentrated in Eastern and central Europe, and less in the British Isles. This leads the editor of these notes to think that the group Miss Austen is referring to is perhaps not a band of Romany. The word "trampers" is used in the next paragraph to further define the group as a band of nomadic beggars and theives.
Note 2: (notice of there being such a set of people in the neighbourhood to Mr. Knightley)
As magistrate of the area, it would fall to Mr. Knightley to maintain the safety of the area. Thus, if it was known that there was a band of beggars harrassing unsuspecting young ladies, Mr. Knightley would be applied to to rectify the situation.