Mammon!
Miss Clack capitalizes mammon as well. Mammon means wealth regarded by an evil influence or false object of worship and devotion. Originated from medical writers as the devil of covetousness. Very strong but accurate, representative word here.
Time
Why does Miss Clack capitalize time? Could it be because she feels so honored/excited to be seen as important/useful to the wealthier members of the family to recall the past that she gives it more value?
The oftener you make them rummage their own minds for a reason, the more manageable you will find them in all the relations of life. It isn’t their fault (poor wretches!) that they act first and think afterwards; it’s the fault of the fools who humour them.
This entire paragraph explicitly states Betteredge's view of women, even his own daughter. This being said, how has he exaggerated when describing all the women previously? We see he holds an obvious bias.
bread and water notwithstanding, she never told you. Self-willed–devilish
Plenty of biblical references with the "bread" and "blood" and many comparisons to the Devil here and earlier on. Previously was mentioned how the Devil works best with those with idle hands, AKA the wealthy. Another possible sign that Betteredge is confident that a wealthy person could commit murder or a "sin".
But compare the hardest day’s work you ever did with the idleness that splits flowers and pokes its way into spiders’ stomachs, and thank your stars that your head has got something it must think of, and your hands something that they must do.
This paragraph goes into depth about the dark methodical nature of the wealthy where they dissect and tear apart things around them because they're restless from having absolutely nothing to do. In the previous paragraph, Betteredge foreshadows that more information about what Mr. Franklin and Miss Rachel do with their time. Is this description of cruelty hint that Betteredge believes someone in the wealthy class (not Miss Rachel or Mr. Franklin, they just set up the idea) is capable of murder and would commit such an act? There's plenty of mention of heads and hands with the dissecting, so could this also hint that a murder was thought out by one (or many) then followed through by them with their own hands? This overall section is very ominous and there is many possible ways that we can hypothesize with the way Betteredge has worded it.
and, between ourselves, he found somebody to do it; and what is more, he throve on it and grew fat on it, and lived happy and died easy on it, dating from the day when my lady took him to church to be married, to the day when she relieved him of his last breath, and closed his eyes for ever
The writing style of Betteredge is very casual with plenty of interjections of their own personal beliefs towards the Herncastles and their situations. It's helpful in the sense that we can get some characteristics of characters and see if they hold true as the novel continues. Betteredge's informality highlights the difference in classes because earlier on we had a narrator that was a part of the wealthy Herncastles that was much more formal. We also get a degree of separation that shows how they are perceived and give us a better idea of the personalities of the family.
I declare, on my word of honour, that what I am now about to write is, strictly and literally, the truth
This lets us know that our narrator(s) are retelling events that happened and will be reflecting throughout the novel. What's interesting is that they say it's nothing but "the truth" but if this novel is all from multiple perspectives, then there is going to be some form of bias with each account. Just something to take into account that this is how they interpreted every event and we, the readers, will most likely have to actively put together some pieces while reading to try to fully understand what happened.