"Supposing a mill with six pairs of stones, two pairs of porcelain roller mills, and the necessary dressing, purifying, and wheat cleaning machinery to require a steam motor of 100 indicated horse power to drive it, then the average consumption of fuel in this mill would be 200 lb. of coal per hour. Such a mill working day and night will turn out about 400 sacks of flour per week of, say, 130 hours, so that 200 × 13 = 26,000 lb. of coal would be required to manufacture 400 sacks of flour. The cost of this quantity of coal may be taken at, say, £12 (about $58.32), and for cost of attending engine and boiler, cost of oil, etc., another £3 (about $14.58) per week may be added; so that, in this case, the manufacture of 400 sacks of flour would cause an expenditure of £15 ($72.90) for the steam motor. Therefore the cost of the steam motor per 20-stone sack of flour may be taken at 9d. (about 18 cents) per sack, if an improved low grinding system is used.

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