Dissatisfied with her maid's cleaning, the lady of the house summons the girl. Running a finger across the top of a cabinet, she holds up her dust-covered finger for the maid to see, saying sternly, "I could write my name in the dust on top of this cabinet."
The maid, glancing at her mistress's finger earnestly replies
"Well, ma'am, isn't it a grand thing to be educated?"
Haha! That's a good one. I love dry humour.