Definition of "therein"

My observation is that whenever one person is found adequate to the discharge of a duty... it is worse executed by two persons, and scarcely done at all if three or more are employed therein.

September 1792, George Washington, letter

"Ha," said Robin, "comest thou from Locksley Town? Well do I know that fair place for miles about, and well do I know each hedgerow and gentle pebbly stream, and even all the bright little fishes therein, for there I was born and bred. Now, where goest thou with thy meat, my fair friend?"

1883, Howard Pyle, chapter V, in The Merry Adventures of Robin Hood […], New York, N.Y.: […] Charles Scribner’s Sons […]

'Behold! once more I kiss thee, and by that kiss I give to thee dominion over sea and earth, over the peasant in his hovel, over the monarch in his palace halls, and cities crowned with towers, and those who breathe therein.'

1886 October – 1887 January, H[enry] Rider Haggard, She: A History of Adventure, London: Longmans, Green, and Co., published 1887