The following estimate of the cost of the power required to manufacture a barrel of flour is taken from the _Miller_. The calculation would hardly hold good in this country owing to difference in cost of fuel attendance etc., but is nevertheless of interest. "The cost of a steam motor per 20 stone (280 lb.) sack of flour depends entirely on local circumstances. It depends first, on the amount of power expended in the production of a sack of flour, that is on its mode of manufacture, and it depends, secondly, on the cost of the necessary amount of power, that is, on the cost of fuel burned per horse power The average consumption of coal of first class steam engines may be taken at 2 lb. per hour per indicated horse power. "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 X 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, L12 (about $58.32), and for cost of attending engine and boiler, cost of oil, etc., another L3 (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 L15 ($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.