Anne is approached by the coal industrialist who wishes to rent the right to mine coal on her land, and, to his surprise, she provides a detailed cost and profit analysis:
You sell your coal in Halifax at eight pence a corve [...] I’m reliably informed that the cost of getting and hurrying to the surface twenty corves of coal is six shillings. That’s seventy-two pence divided by twenty, that’s thruppence ha’penny per corve. Which means you make four-pence ha’penny clear gain. Per corve. So let’s times that by five and we have one shilling and ten pence ha’penny - or twenty two pence - per square yard. Four thousand eight hundred and forty square yards in an acre, times twenty-two, and your clear gain per acre is four hundred and fifty three pounds and fifteen shillings.
Just to put that in perspective: a family of 5 could live quite comfortably for bit over 1 pound per week while spending about 2 shillings on coal and the life savings of Anne's elderly father (a landowner and retired officer) were around 450 pounds.
It is bit unclear is the number presented above a total income from an acre of field or just an annual one, but since Anne is tempted to open her own mine, with the initial cost of 2000 pounds that (according to her advisor) would be quickly paid off, it seems that this might be an annual rather than total income.
I've found this study that shows the fortnightly wage for a minter around 1835 to about 300 pences per fortnight (or 12.5 shillings per week)1
Are those details about coal mining revenue reliable?
1 For a help with currency conversion, let me quote Terry Prattchett:
Two farthings = One Ha'penny. Two ha'pennies = One Penny. Three pennies = A Thrupenny Bit. Two Thrupences = A Sixpence. Two Sixpences = One Shilling, or Bob. Two Bob = A Florin. One Florin and One Sixpence = Half a Crown. Four Half Crowns = Ten Bob Note. Two Ten Bob Notes = One Pound (or 240 pennies). Once Pound and One Shilling = One Guinea.
The British resisted decimalized currency for a long time because they thought it was too complicated.”
Here is a chart:
|Shillings & Pence (s. / d.)||Pence Equiv.||Coin / Note Name|
|0 / ¼||¼ d.||Farthing|
|0 / ½||½ d.||Ha'penny (Half-Penny)|
|0 / 1||1 d.||Pence|
|0 / 2||2 d.||Tuppence (Two-Pence)|
|0 / 3||3 d.||Thruppence (Three-Pence)|
|0 / 6||6 d.||Sixpence|
|1 / 0||12 d.||Shilling or Bob|
|2 / 0||24 d.||Florin|
|2 / 6||30 d.||Half a Crown|
|5 / 0||60 d.||Crown (Five Shillings/Bob)|
|10 / 0||120 d.||Ten Bob (Note)|
|20 / 0||240 d.||Pound (Note) (£)|
|21 / 0||252 d.||Guinea (Coin)|