The background of the missionaries in these chapters is not explicitly explained. Instead, it can be inferred based on parallel plot. A parallel plot is a one more story line that seem to have nothing in common with the lead story line, but it is usually contains additional information or background of an event or a character which makes a story be more deep.
They give the piece a dreary, melancholy tone.
The imagery of these quotes are very dark and gloomy. They change the author's tone into a more dreary, melancholy tone.
In all of his writings, Elie wiesel always choose memoir/fiction as his genre.
Including the fact that he based it on his own life (for those who don't know, Elie wiesel is a survivor of holocaust and write books about it), it helped people empathize and can easily accept his point of view toward the incident.
In the following excerpt of "Sinners in the hands of an angry God", Edwards extensively compares God's wrath with great Warters:
"The Wrath of God is like great Waters that are dammed for the present; they increase more and more, & rise higher and higher, till an Outlet is given, and the longer the Stream is stop’d, the more rapid and mighty is it’s Course, when once it is let loose. 'Tis true, that Judgment against your evil Works has not been executed hitherto; the Floods of God’s Vengeance have been with-held; but your Guilt in the mean Time is constantly increasing, and you are every Day treasuring up more Wrath; the Waters are continually rising an waxing more and more mighty; and there is nothing but the meer Pleasure of God that holds the Waters back that are unwilling to be stopped, and press hard to go forward; if God should only withdraw his Hand from the Flood-Gate, it would immediately fly open, and the fiery Floods of the Fierceness and Wrath of God would rush forth with inconceivable Fury, and would come upon you with omnipotent Power; and if your Strength were ten thousand Times greater than it is, yea ten thousand Times greater than the Strength of the stoutest, sturdiest, Devil in Hell, it would be nothing to withstand or endure it."